The total sales of a company (in millions of dollars) t months from now are given by the following formu S(t)=7t+1 (A) Use the four-step process to find S'(t). (B) Find S(15) and S'(15). (C) Use the results in part (B) to estimate the total sales after 16 months and 17 months. (A) S'(t) = (B) S(15)= (Type an integer or a decimal