this question: I point(s) p The total revenue (in hundreds of dollars) from the sale of x spas and y solar heaters is approximated by R(x,y) = 10+ 258x + 220y - 6x2-5y -6xy. Find the number of each that should be sold to produce maximum revenue. Find the maximum revenue. . .. .. Find the derivatives Rxx, Ryy, and Rxy- Rxx = . Ry = ]. Rxy = Selling spas and solar heaters gives the maximum revenue of $ (Simplify your answers.)