We saw that the profit (in thousands of dollars) that Aunt Mildred’s Metalworks earns from producing x tons of steel and y tons of aluminum can be approximated by P(x, y) = 36xy - x³ - 8y³. If the amount of steel produced varies from 0 to 8 tons, and the amount of aluminum produced varies from 0 to 4 tons, find the average profit.