The angular momentum of a rotating wheel is 7.5 kg·m²/s at t = 0 s, stays at that value until t = 3.0 s, and then decreases linearly to −2.5 kg·m²/s at t = 8.0 s.
Calculate the average net external torque acting on the wheel during the time interval from t = 3.0 s to t = 8.0 s.