Optimization application prob

A large storage tank is to be built in the shape of a cylinder. Assume the following facts about the cost:

Cost of the floor is $12/sq ft

Cost of the curved side wall is 1.8 times the cost of the floor

Cost of the roof is 2.6 times the cost of the floor

a) If the total volume is fixed at 1.2 million cu ft, what is the cost of the cheapest tank to construct?

b) Compute the ratio of height to diameter for the cheapest tank.

I stink at these....any help would be appreciated.

~CC