Delco contractors create six-month rolling schedules, which are recomputed monthly. For competitive reasons (they would need to divulge proprietary design criteria, methods, and so on), Delco does not subcontract. Therefore, its only options to meet customer requirements are (1) work on regular time; (2) work on overtime, which is limited to 30 percent of regular time; (3) do customers; work early, which would cost an additional $5 per hour per month; and (4) perform customers' work late, which would cost an additional $10 per hour per month penalty, as provided by their contract. Delco has 25 engineers on its staff at an hourly rate of $30. The overtime rate is $45. Customers' hourly requirements for the six months from January to June are

January 5,000
February 4,000
March 6,000
April 6,000
May 5,000
June 4,000

Develop an aggregate plan using a spreadsheet. Assume 20 working days in each month.