Answer:
[tex]F(x)=\left\{\begin{array}{cl}15(40-x)&\text{if $0<x<40$}\\0&\text{if $40\le x\le65$}\\15(x-65)&\text{if $x>65$}\end{array}\right.[/tex]
Step-by-step explanation:
(a) For x below 40, the number of miles per hour below 40 is (40-x). Then the fine for that speed is 15(40 -x).
For x between limits, the fine is zero.
For x above 65, the number of miles per hour above 65 is (x-65). Then the fine for that speed is 15(x -65).
[tex]F(x)=\left\{\begin{array}{cl}15(40-x)&\text{if $0<x<40$}\\0&\text{if $40\le x\le65$}\\15(x-65)&\text{if $x>65$}\end{array}\right.[/tex]
