A person is doing leg lifts with 3.00-kg ankle weights. The lower leg itself has a mass of 5.00 kg. When the leg is held still at an angle of

30.0° with respect to the horizontal, the patellar tendon pulls on the tibia with a force of 321 N at an angle of 20.0° with respect to the lower leg. Assume the force exerted on the tibia by the femur is the only other significant force acting on the lower leg. Find the magnitude of the force exerted on the tibia by the femur.