A 320-G Ball and a 400-G Ball Are $0.00070 \mathrm {~N} \cdot \mathrm { m }$

Multiple Choice

A 320-g ball and a 400-g ball are attached to the two ends of a string that goes over a pulley with a radius of 8.7 cm. Because of friction in its axle, the pulley does not begin to rotate. What is the magnitude of the frictional torque at the axle of the pulley if the system remains at rest when the balls are released?

A) $0.00070 \mathrm {~N} \cdot \mathrm { m }$
B) $0.61 \mathrm {~N} \cdot \mathrm { m }$
C) $0.068 \mathrm {~N} \cdot \mathrm { m }$
D) $0.063 \mathrm {~N} \cdot \mathrm { m }$
E) $0.079 \mathrm {~N} \cdot \mathrm { m }$