Answer Happy

“produceCo” wants to plan its production of two products with
seasonal demands over a 12-month period. The monthly demand of
product A is 100 units during the months of January, February, and
March; 30 units during the months of April, May, June, and July;
and 20 units during the remaining months. The demand of product B
is 50 during the months of January through May and 15 during the
remaining months. The company should meet the demands on-time. The
demand can be met from current months production or from the
productions of the previous months. Initial inventory level of
product A and B are 50 and 30, respectively. Suppose that the unit
product cost of Product A and B is 4.00 TL and 6.00 TL,
respectively, provided that these were manufactured till August. In
September, the unit costs are increased to 6.00 TL and 8.00 TL
because of the cost increase in raw materials. The total
manufactured units of product A and B (Product A + Product B) in a
month cannot exceed 150 in Jan-Mar, and 90 in Apr-Dec. Furthermore,
each unit of product A occupies 3 cubic feet, and each unit of item
B occupies 2 cubic feet of inventory space. Suppose that the
maximum inventory space allocated to these products is 90 cubic
feet and the holding cost per cubic foot during any month is 0.30
TL.
Solve model using GAMS