A rotating shaft with an applied torque of 400 Newton-meters is held in place (stopped) by a shaft key. The diameter of the shaft is 15 centimeters. The shaft key has a length of 20 cm, and is square, with its width and height being 5 cm. Calculate the following:
(a) the force on the shaft key
(b) the shear stress on the shaft key
(c) the bearing stress on the shaft key