A "Dynamic" (Multi-Period) Production Problem: Footballs

The Pigskin company will produce footballs over the next six months.  Forecasted demand and production costs over this time period are:

Month 1 2 3 4 5 6
Demand
(Cases of 100)
100 150 300 350 250 100
Unit Production Cost $ 12.50 $ 12.55 $ 12.70 $ 12.80 $ 12.85 $ 12.95

Pigskin has a monthly production capacity of 300 cases.  They currently has 50 cases of footballs in inventory, and has enough capacity to store up to 100 cases.  The holding cost of keeping a football in inventory for a month is estimated to be 5% of the cost of producing in that month. 

Pigskin has decided that they want to meet the entire demand for footballs over the 6-month period.  How can they do that at minimum cost?