A firm wants to determine the amount of frictional torque in their current line of grindstones, so they can redesign them to be more energy efficient. To do this, they ask you to test the best-selling model, which is basically a diskshaped grindstone of mass 1.4 kg and radius 6.40 cm which operates at 750 rev/min. When the power is shut off, you time the grindstone and find it takes 43.8 s for it to stop rotating.
(b) What is the frictional torque exerted on the grindstone? in N·m