A certain dealer owns a warehouse that can store a maximum of 600 units of a given commodity. He has on hand 100 units of the commodity and knows the buying and selling price for the next 5 time periods. They are:

PERIOD	BUYING PRICE	SELLING PRICE
1	15	16
2	17	17
3	21	20
4	19	19
5	16	20

He is permitted to sell up to the amount that he has in his warehouse at the beginning of each period. If he buys in a given period, delivery will be made so that it is in storage at the beginning of the next period. Let (X_i, Y_i) denote the amount he buys and sells in time-period i respectively. What is the optimal buying\selling strategy.

Formulate the linear programming problem.

Develop a spreadsheet and solve the problem.