Please find parts A-D please

The sales of a new high-tech item (in thousands) are given by the following function, where t represents time in years. Find the rate of change of sales at each time. S(t) =97 - 90 e - 0.4t (a) After 1 year. (b) After 5 years. (c) What is happening to the rate of change of sales as time goes on? (d) Does the rate of change of sales ever equal zero? (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? O A. First it decreases, then it' increases. O B. First it increases, then it decreases. O C. It always decreases. O D. It always increases (d) Does the rate of change of sales ever equal zero