The position of an airplane at time ???? is given by ????(????)=????(????)=2????9/2 and ????(????)=????(4−????) from take-off at ????=0 and landing at ????=4. The gravitational force is ????(????,????,????)=(0,0,−????????), where ???? is the mass of the airplane and ???? the gravitational constant. Find the work done by the gravitational force on the airplane during the flight.