A company determines that monthly sales S(t), in thousands of dollars, after t months of marketing a product is given by S(t) = 23-551 + 230t+ 160. a) Find S'(1), S'(2), and S'(4). b) Find S''(1), S''(2), and S''(4). c) Interpret the meaning of your answers to parts (a) and (b). (a) First, find S'(t). S'(t)=