Physics???

[Timothy J]

A disk-shaped grindstone (I = MR^2/2) of mass 1.7kg and radius 8cm is spinning at 730rev/min. The power is shut off, an axe blade is held against the grindstone, and the grindstone comes to rest in 9s. Find the torque exerted on the axe blade by the grindstone.

A) 0.16N-mB) 0.26C) 0.37D) 0.45E) 0.05

[Doctor Q]

Answer is E) 0.05