2. A store is having a 12-hour sale. The total number of shoppers who have entered the store f hours after the sale begins is modeled by the function S defined by S(t) = 0.514 - 16t + 144t for 0 S t $ 12. At time f = 0, when the sale begins, there are no shoppers in the store. (a) At what rate are shoppers entering the store 3 hours after the start of the sale