Formulate the aggregate plan using linear programming and solve it using Solver.

Using the variables R = ; O = ;
S = ; I = ; EI = ending inventory
Min Cost = 5R + 7.5O + 9S + 2I

Subject to:
O ≤ 300
S ≤ 300
EIi ≥ 0 for all periods i = 1 to 5
regular productioni ≤600 for all periods i = 1 to 5

   January   February   March   April   May
Forecast   500   750   1200   650   300
Beginning Inventory   100   200   50   0   0
Regular Time   600   600   600   600   300
Overtime   0   0   250   50   0
Subcontracting   0   0   300   0   0
Ending Inventory   200   50   0   0   0

The total cost of this plan is $18,950, with $13,500 spent on regular production, $2,250 on overtime production, $2,700 on subcontracting, and $500 on ending inventory charges.