9514 1404 393
Answer:
d. $30
Explanation:
When price and demand are linearly related like this, revenue is a quadratic function. Its maximum will be halfway between the prices that give a revenue of 0. Those prices are $60 (where demand is 0) and $0 (where demand is irrelevant). The halfway point is ($60 +0)/2 = $30.
As a check, you can figure revenue for some nearby points.
at $30, revenue is ($30)(15) = $450
at $24, revenue is ($24)(18) = $432
at $36, revenue is ($36)(12) = $432
This confirms revenue is maximized at a price of $30.