$2)$

A load is to be raised $6$ m by the hoisting system shown. Assuming gear $A$ is initially at rest, accelerates uniformly to a speed of $120$ rpm in $5$ s $,$ and then maintains a constant speed of $120$ rpm $,$ determine $($a$)$ the number of revolutions executed by gear $A$ in raising the load, $($b$)$ the time required to raise the load.