ashley is doing a knee extension exercise. She uses a 200 N weight strapped to her ankle 40 cm from her knee joint. She holds her leg so that the horizontal distance from her knee joint to the weight is 30 cm. The calf and the attached weight are held in place by the knee extensor muscles, which have a moment arm of 4.0 cm about the knee joint axis. How much extra force, beyond the force that holds the calf in place, must these muscles produce to hold the weight in the position described