a)Using the given information we can set the following equation:
[tex]C=0.20n+15[/tex]
b) The graph of the linear equation above for up to and including 200 minutes is as follows:
Which corresponds to option B.
c) If n=40 then:
[tex]C=0.20\cdot40+15=8+15=23[/tex]
Then the total monthly cost is $23.
d) If C=30, solving the first equation on the board for n we get:
[tex]\begin{gathered} 30=0.20n+15 \\ 0.20n=15 \\ n=75 \end{gathered}[/tex]
Then the number of minutes is 75.
