(a) In Example 5, find the total sales for January 10, and determine the rate at which sales are falling on that day.

(b) Compare the rate of change of sales on January 2 (Example 5) to the rate on January 10. What can you infer about the rate of change of sales?

Example 5

At the end of the holiday season in January, the sales at a department store are expected to fall (Fig. 3). It is estimated that for the x day of January the sales will be

S(x) = 3 + 9 (x + 1) thousand dollars.