The sales of a new high-tech item (in thousands) are given by S(t) = 100 - 90 e - 0.4t where t represents time in years. Find the rate of change of sales at each time. a.) After 1 year. b.) After 5 years. c.) What is happening to the rate of change of sales as time goes on? d.) a. The rate of change after 1 year is thousand items per year. (Round to three decimal places as needed.) b. The rate of change after 5 years is |thousand items per year. (Round to three decimal places as needed.) c. What is happening to the rate of change of sales as time goes on? A. It always decreases. O B. First it decreases, then it increases. O C. It always increases. O D. First it increases, then it decreases