Answer
The cost function in dollars is $C(x)=0.4x+70$
The revenue function is $R(x)=0.5x$
The profit function is $P(x)=0.5x-(0.4x+70)=0.1x-70$
Work Step by Step
The cost function is the following:
We have a fixed cost of $\$70$ in an edition.
We have a marginal cost odf $40$ cents per copy.
The cost function in dollars is $C(x)=0.4x+70$
The revenue function is $R(x)=0.5x$, as a copy costs $50$ cents.
The profit function equals to $R(x)-C(x)$, here it is:
$P(x)=0.5x-(0.4x+70)=0.1x-70$
