Answer:
$450
Step-by-step explanation:
The number rented (q) as a function of the price (p) is ...
q = 100 -(p-400)/5 = 180 -p/5
Then the monthly revenue is ...
r(p) = pq = p(180 -p/5) = (1/5)(p)(900 -p)
This equation describes a downward-opening parabola with zeros at p=0 and p=900. The p-coordinate of the vertex of the parabola (price for maximum revenue) is halfway between these zeros, at p=450.
To maximize revenue, monthly rent should be $450.
_____
Maximum revenue will be 90·$450 = $40,500. Revenue is currently $40,000.
