Answer
The work done on the stone is $151~J$
Work Step by Step
We can find the work done on the stone:
$Work = \tau ~\Delta \theta$
$Work = r~F ~\Delta \theta$
$Work = (0.10~m)(20.0~N)(12~rev)(2\pi~rad/rev)$
$Work = 151~J$
The work done on the stone is $151~J$.
