Elena, a black belt in tae kwon do, is experienced in breaking boards with her fist. A high-speed video indicates that her forearm is moving with a rotational speed of 40 r a d / s 40rad/s when it reaches the board. The board breaks in 0.0040 s 0.0040s and her arm is moving at 20 r a d / s 20rad/s just after breaking the board. Her fist is 0.32 m 0.32m from her elbow joint, and her forearm rotational inertia is 0.050 k g ⋅ m 2 0.050kg⋅m 2 What is the average force the board exerts on her fist while breaking the board (equal in magnitude to the force that her fist exerts on the board)? I exerts on her arm during the break.