Answer
a. $y_1=30+5x$, $y_2=7.5x$ dollars.
b. See graph.
c. $(12,90)$, $x=12$ hours, $y=90$ dollars.
d. See explanatioins.
Work Step by Step
a. For option-1, we have $y_1=30+5x$ and for option2, we have $y_2=7.5x$ dollars.
b. See graph.
c. The intersection can be found at $(12,90)$ and it means that at $x=12$ hours, the two cost will be both equal to $90$ dollars.
d. We can verify part-c by letting $y_1=y_2$ which gives $30+5x=7.5x$. Subtract $5x$ from both side to get $30=2.5x$ and we have $x=30/2.5=12$ hours. and $y_1=y_2=30+5\times12=90$ dollars at this point.
