Simplify the Difference Quotient for the Linear Function $f(x)$ , and Use It to Identify the Rate of Change

Multiple Choice

Simplify the difference quotient for the linear function $f(x)$ , and use it to identify the rate of change of the function.
- $f(x) =-3 x+2000$

A) 3
B) 2000
C) -2000
D) -3