1. A disk drive manufacturer is in need of an aggregate plan for July to December. The company has gathered the following data:

Month	Demand	Month	Demand
July	400	Oct	700
Aug	500	Nov	800
Sep	550	Dec	700

Item	Cost
Materials	$35/disk
Inventory	$8/disk/month
Subcontracting	$80/disk
Stock-out	$15/disk
Regular time labor	$12/hour
Overtime labor	$18/hour (above 8 hrs)
Hiring cost	$40/worker
Layoff cost	$80/worker

Other data include:

Item	Data
Current workforce (June)	8 people
Labor hours per disk	4 hrs
Workday per month	20 days
Beginning inventory	150 disk
Ending inventory requirement	0

1. Prepare the aggregate plan for varying workforce, no subcontract, and no stock-out during December. Overtime limit is 20 hours per worker per month.

Month	Hired	Laid off	Workforce	Inventory	Production
July
Aug
Sep
Oct
Nov
Dec

b) How much is the total regular time cost?

c) The manufacturer decides to revise its plan and maintain its current workforce to produce the requirement. Overtime limit is still 20 hours per worker per month while ending inventory should be equal to the beginning inventory. Prepare the aggregate plan under the condition.

Month	Overtime	Inventory	Stockout	Subcontract	Production
July
Aug
Sep
Oct
Nov
Dec

d) Is the revised schedule better than the original plan? Why?