Question 1171476
(18+3x)(36-3x)=revenue ,where x is the number of increases of $3 in price.
648+54x-9x^2=revenue
maximize when x=-b/2a=-54/-18 or 3
$27 is the price at maximum revenue
27  is the numbers of frames sold for maximum revenue.
The answer is $27, the maximum revenue is $729.