To prevent pests, an orchard can have no more than 9 times as many apple trees as peach trees. Also, the number of apple trees plus 3 times the number of peach trees must not exceed 420. The revenue from a single apple tree is $172 and the revenue from a single peach tree is $513. Determine the number of each type of tree that will maximize revenue. What is the maximum revenue? Let x represent the number of apple trees and y represent the number of peach trees.