A retail appliance store sells 4,000 television sets each year. It costs $8 to store one television set for a year. To reorder, there is a fixed processing cost of $25, plus a $7.5shipping fee for each television set. (a) The cost function, in dollars, expressed as a function of

x

, the number of television sets the store reorders each time (

x

is also the lot size the store must maintain), is

C(x)=

, where

x

is defined between and . (b) To minimize its cost, the lot size the store maintains should be television sets, and the store should place orders each year. (Your answers should be integers. )