A 3.73-m long thin seesaw with a mass of 43.7 kg has a pivot in its center. Two children with masses 35.9 kg and 30.7 kg sit on extreme opposite ends and start moving up and down. When the seesaw is horizontal and neither child is in contact with the ground, what is the magnitude of the net torque acting on the board (use units of N*m)? What is the magnitude of the angular acceleration of the seesaw at this instant (use units of rad/s^2)?