TOBB ETÜ 2014-2015 Spring Semester
END 307- Production Systems Planning
Assignment 6
Assignment Date: 12.03.2014, Submission Date: 19.03.2014
1. Suplash Inc. produces soft drinks. Soft drink sales are somewhat seasonal and Suplash wants to plan its workforce levels and production on April 30th for the next 5 months. The demand forecasts for the total demand across all types of drink are given in the following table in terms of cases.
Month
May
June
July
August
September
Production Days
(round to nearest integer)
20+(FactorX x 4)
20+(FactorX x 4)
18+(FactorX x 3)
16+(FactorX x 3)
22+(FactorX x 3)
Forecasted Demand
(round to nearest integer)
9300+(FactorX x 300)
12200+(FactorX x300))
17200+(FactorX x 400)
13000+(FactorX x 400)
6300+(FactorX x 400)
As of April 30 th , Suplash has 86 workers on payroll. Over a period of 26+(Factor X x 5) working days (7 hours working days) when there were 100 workers in the payroll, Suplash produced 12000 cases of soft drink. The cost to hire each worker is $155 and the cost of laying off each worker is $400.
Holding costs amount to 0.75 $ per case per month. As of April 31, Suplash has 3500 cases of drink in stock. It plans to start October with 3000 cases on hand. Assume that each worker gets paid $1450+
(FactorX x 150) monthly on regular time. (For all FaxtorX xY terms, round the result to nearest integer) a. Based on this information, find the minimum constant workforce plan for Suplash. Determine hiring, firing, and holding cost for that plan. b. Determine the minimum inventory plan and the cost of that plan. c. Determine a plan where the company keeps constant workforce at the level of the average number of workers from the chase strategy found in part (b), and any excess demand is satisfied from overtime production. It cost 18 $/hour in overtime. (All the excel models covered in class is available in the website) d. Develop the explicit mathematical optimization model for the problem (including over time option) and write it down. (hint: You need to first find cost of producing one case in over time) e. Transfer your model to Excel and find the optimal (integer) solution to the problem. (include the print out of the model and the results from excel in your HW) g. Modify your optimization model in part (d) to consider backordering. Backordering cost per case is estimated to be $4 per case. Write down the new model (no need to transfer to Excel).

2. Fill in the gap;
Aggregate planning is about ……..
The key point in defining aggregate unit is that ……
To do aggregate planning is important because …
(Submit your written hw in class. Send your excel file for optimization to both TAs. Name your excel file st_1 st student ID_2 nd student ID.xls. You must hand in printed/prepared HW)