Chapter 1.7, Problem 43E

Sales at a Department Store Let $S\left(x\right)$ represent the total sales (in thousands of dollars) for the month $x$ in the year $2005$ at a certain department store. Represent each following statement by an equation involving $S$

or $S\text{'}$.

a. The sales at the end of January reached $\$120,560$ and were rising at the rate of $\$1500$ per month

b. At the end of March, the sales for this month dropped to $\$80,000$

and were falling by about $\$200$ per day. (Use $1$ month $=30$

days.)