The Cessna model $310$ twin$-$engine propeller$-$driven airplane is powered by two Continental IO$-520-$M engines rated at $285$ hp each at $2,700$ rpm at sea level. McCauley three$-$blade propellers are used, with a diameter of $6\mathrm{.}27$ ft$.$ The maximum speed of the airplane at sea level is $238$ mi$/$h$.$ Assume the performance of the propeller is given by the propeller efficiency curves in Fig. $3\mathrm{.}7,$ and that the propellers are variable$-$pitch so as to obtain the maximum efficiency. Calculate the maximum horsepower available from the engine$-$propeller combination at sea level.