ID ________________________ Name ____________________________ Page 1 of 9
BP 6904 Operations Management Comprehensive Exam Guideline These are the list of practices questions for comprehensive exam. The exam will be given in the similar format. Students will need 1 hour. Problem 1: The associate administrator at ABAC Hospital wants to evaluate the layout of the outpatient clinic. The following table shows the interdepartmental flows (patients/day) between departments. Trips Between Departments Department 1 2 3 4 5 6 1. Reception 15 20 5 10 15 2. Business Office 10 5 10 15 3. Examining room 15 20 20 20 4. X-Ray 25 10 5. Laboratory 10 20 6. Surgery 5 If the current layout is as follow: 4 6 5 2
3
1
a. Determine the effectiveness of the current layout (as measured by the non-adjacent load). b. Try to find the best possible layout if it must be revised to keep department 1 at its present location. Determine the total non-adjacent load obtained. (Try the following layout) 4 5 2 6
3
1
(Chapter 7) [15 marks]
Two-way load 1<->2=15+10=25 1<->3=20+15=35 1<->4=5+0=5 1<->5=10+0=10 1<->6=15+0=15
2<->3=5+0=5 2<->4=10+0=10 2<->5=15+0=15 2<->6=0+0=0
3<->4=20+0=20 3<->5=20+10=30 3<->6=20+0=20
4<->5=25+0=25 4<->6=10+5=15
5<->6=20+0=20
a. Original layout 15 5 25 4 10
2
15 20
5
6
20
20
15
3
35
5 30
10
1
25
Total non-adjacent load = 15+5+25+25 = 70 b. New layout (Hint: Try to reduce maximum non-adjacent load in the original layout (1<->2 = 25 and 4<->5 =25))
ID ________________________ Name ____________________________ Page 2 of 9
5 10 4 15
25
5 20
20
15
30
25 5
6
20
2
3
10 35
15
Total non-adjacent load = 5+10+15 = 30
1
ID ________________________ Name ____________________________ Page 3 of 9 Problem 2: A company is setting up an assemble line to produce 192 units per eight-hour shift. The following table identifies the work elements, times, and immediate predecessors. Work Element Time (sec) Immediate Predecessor(s) A 40 B 80 A C 30 D, E, F D 25 B E 20 B F 15 B G 120 A H 145 G I 130 H J 115 C, I Total 720 a. Draw a precedence diagram. b. What is the desired cycle time? c. What is the theoretical minimum number of work stations? d. Balance the line, and show your solutions on your precedence diagram. e. What is the efficiency of the solution found? (Chapter 7) [20 marks]
Solution a. Precedence Diagram D 25 B 80 A 40
E 20
C 30 J 115
F 15 G 120
H 145
I 130
b. Desired Cycle time Cd = (8 hours x 60 min. x 60 sec.) / 192 units = 150 seconds/unit c. N = 720 / 150 = 4.8 or 5 stations d. Workstation 1 2 3 4 5
Work Elements A, B, D G, E H I, F C, J
Cumulative Time 145 140 145 145 145
D 25 B 80 A 40
E 20
C 30 J 115
F 15 G 120
H 145
I 130
Ca = 145 seconds e. Efficiency = 720 / (5 x 145) = 0.9931 = 99.31%
Idle Time 5 10 5 5 5
ID ________________________ Name ____________________________ Page 4 of 9 Problem 3: (Chapter 9)
The following table shows all activities required to complete a project. Task Time (weeks) Precedence Task(s) A 12 B 10 C 3 A, B D 23 C E 17 C F 8 E G 12 C H 8 G I 5 D, H, F 8.1. Draw the network and calculate ES, LS, EF, and LF. 8.2. Find the total number of paths in this project network. 8.3. What is the project completion time? 8.4. Identify the critical activities. 8.5. Identify all jobs that have slack and also show the number of slack of each job. 8.1. D 23
A 12
0
12
0
12 C 3
B 10
0
10
2
12
12
15
12
15
E 17
G 12
15
38
17
40
15
32
15
32
15
27
20
32
8.2. There are 6 paths: 1. A-C-D-I, 2. A-C-E-F-I, 3. A-C-G-H-I, 4. B-C-D-I, 5. B-C-E-F-I, 6. B-C-G-H-I 8.3. 45 weeks 8.4. A, C, E, F, I 8.5. B =2, D=2, G =5, H=5
F 8
H 8
32
40
32
40
27
35
32
40
I 5
40
45
40
45
ID ________________________ Name ____________________________ Page 5 of 9 Problem 4: Fill in the forecasted data of each period. Month Sales By 3-month average By 4-month average 1 10 2 12 3 14 4 16 12.0 5 14 14.0 13.0 6 15 14.7 14.0 7 13 15.0 14.8 8 15 14.0 14.5 9 14 14.3 14.3 10 19 14.0 14.3 11 20 16.0 15.3 12 12 17.7 17.0 Which method gives the superior forecasted data? Solution Calculate Mean Absolute Deviation (MAD) MAD of 3MAD of 4-month By 4Month Sales By 3month average average month month (5) = |(2)-(3)| (6) = |(2)-(4)| average (1) (2) average (4) (3) 1 10 2 12 3 14 4 16 12.0 4.0 5 14 14.0 13.0 0.0 1.0 6 15 14.7 14.0 0.3 1.0 7 13 15.0 14.8 2.0 1.8 8 15 14.0 14.5 1.0 0.5 9 14 14.3 14.3 0.3 0.3 10 19 14.0 14.3 5.0 4.8 11 20 16.0 15.3 4.0 4.8 12 12 17.7 17.0 5.7 5.0 Mean 2.48 2.38 Since the MAD of 4-month average is less than those of the 3-month, the 4-month average is a better choice.
ID ________________________ Name ____________________________ Page 6 of 9 Problem 5:
Mama’s Stuffin’ is a popular food item during the fall and winter months, but it is marginal in the spring and summer. Use the following demand forecasts and costs to determine which of the following production planning strategies is best for Mama’s Stuffin’: a. Level production over the 12 months b. Produce to meet demand each month. Absorb variations in demand by changing the size of the workforce. c. Keep the workforce at its current level. Supplement with overtime and subcontracting if necessary. d. What is the cheapest plan? Month Demand forecast (pallet) 1 2000 2 1000 3 1000 4 1000 5 1000 6 1500 7 2500 8 3000 9 9000 10 7000 11 4000 12 3000 Overtime capacity per month = regular production Subcontracting capacity per month = unlimited Regular production cost = $30 per pallet Overtime production cost = $40 per pallet Subcontracting cost = $50 per pallet Holding cost = $2 per pallet Beginning workforce = 10 workers Production rate = 200 pallets per worker per month Hiring cost = $5000 per worker Firing cost = $8000 per worker
Solution a. Total yearly demand = 36,000 pallets, therefore, average demand = 36,000 / 12 = 3,000 Total worker needed = 3,000 / 200 = 15 workers. Need more = 15 – 10 = 5 workers Month Demand forecast (pallet) Production Plan Inventory 1 2,000 3,000 1,000 2 1,000 3,000 3,000 3 1,000 3,000 5,000 4 1,000 3,000 7,000 5 1,000 3,000 9,000 6 1,500 3,000 10,500 7 2,500 3,000 11,000 8 3,000 3,000 11,000 9 9,000 3,000 5,000 10 7,000 3,000 1,000 11 4,000 3,000 0 12 3,000 3,000 0 Total 36,000 36,000 63,500 Total cost = (36,000 x $30) + (63,500 x $2) + (5 x $5,000) = $1,232,000
ID ________________________ Name ____________________________ Page 7 of 9 b. Month 1 2 3 4 5 6 7 8 9 10 11 12 Total
Demand forecast (pallet) 2,000 1,000 1,000 1,000 1,000 1,500 2,500 3,000 9,000 7,000 4,000 3,000 36,000
Production Plan
Workers Needed
Workers Hired
Workers Fired
2,000 1,000 1,000 1,000 1,000 1,500 2,500 3,000 9,000 7,000 4,000 3,000 36,000
10 5 5 5 5 8 13 15 45 35 20 15
0 0 0 0 0 3 5 2 30 0 0 0
0 5 0 0 0 0 0 0 0 10 15 5
181
40
35
Total cost = (36,000 x $30) + (40 x $5,000) + (35 x $8,000) = $1,560,000 c. Regular capacity = 2000 pallets Overtime = 2000 pallets Month Demand forecast Production Plan (pallet) 1 2,000 2000 2 1,000 1,000 3 1,000 1,000 4 1,000 1,000 5 1,000 1,000 6 1,500 1,500 7 2,500 2,500 8 3,000 3,000 9 9,000 9,000 10 7,000 7,000 11 4,000 4,000 12 3,000 3,000 Total 36,000
Regular Capacity 2,000 1,000 1,000 1,000 1,000 1,500 2,000 2,000 2,000 2,000 2,000 2,000 19,500
Overtime
500 1,000 2,000 2,000 2,000 1,000 8,500
Total cost = (19,500 x $30) + (8,500 x $40) + (8,000 x $50) = $1,325,000 d. Plan A is the cheapest.
Subcontract
5,000 3,000
8,000
ID ________________________ Name ____________________________ Page 8 of 9 Problem 6:
The James-75 Carpet Discount Store in Banglampoo stocks carpet in its warehouse and sells it through an adjoining showroom. The store keeps several brand and styles of carpet in stock; however, its biggest seller is Super Shag carpet. The store wants to determine the optimal order size and total inventory cost for this brand of carpet given an estimated annual demand of 10,000 yards of carpet, an annual carrying cost of $0.75 per yard, and an ordering cost of $150. The store would also like to know the time between orders given that the store opens 300 days a year. (Hint: find EOQ)
Demand = Carrying cost = Order cost =
10000 0.75 150
Solution 2C o D 2(10000)(150) = = 2000 yards Cc 0.75 Time Between Order = (2000/10000) x 300 = 60 (working) days (The company has to order every time 2000 yards at every 60 (working) days.) Qopt =
ID ________________________ Name ____________________________ Page 9 of 9 Problem 7:
We have seen the role of information and information technology, the supply chain management, and lean manufacturing, for Toyota and 7/11 cases. Please discuss in detail how to utilize the IT, Supply Chain Management concept, and Lean Manufacturing concept in MK restaurant? Problem 8:
The chase strategy and the level strategy represent two extremes in aggregate planning. Describe the type of environment in which each would work best.
