Campbell's sells used trailers, U, and new trailers, N, Its profits are given by p = 100N+68U-5N^2-5U^2-2NU. The profit-maximizing combination of trailers for Campbell's is: (A) N= 9 and U = 5. (B) N=7 and U=7 (C) N=5 and U=9 (D) N=13 and U=0 (E) N=9 and U=9.
If at all possible, please show some of the work so that I at least know how to set up this problem correctly. I do truly want to learn how to do this type of problem but the book we have is not very helpful and I am having trouble finding an example on YouTube where I can watch someone walk through it.