Astore charges their customers based on the number of items that they buy. jane bought four items and was charged $15 and george bought twelve items and was charged $39. write a function to model the cost based on the number of items you buy. then determine how much you bought if you were charged $33. a) f(x) = 3x + 3; f(10) = 33 b) f(x) = 3x + 3; f(33) = 102 c) f(x) = 1/3x + 3; f(90) = 33 d) f(x) = 1/3x + 3; f(33) = 14