A flight attendant pulls her 70 N flight bag a distance of 390 m along a level airport floor at a constant velocity. The force she exerts is 39 N at an angle of 56° above the horizontal. (a) Find the work she does on the flight bag. J(b) Find the work done by the force of friction on the flight bag. J(c) Find the coefficient of kinetic friciton between the flight bag and the floor.