I'm guessing the angle is supposed to have measure 60º, not 600º... In this case,
[tex]\dfrac\ell{2\pi(21\,\mathrm m)}=\dfrac{60^\circ}{360^\circ}[/tex]
That is, the length of the arc we care about [tex](\ell)[/tex] occurs with the circle's circumference in the same ratio as the measure of the central angle it subtends occurs with one complete revolution of the circle. Then with [tex]\pi=\dfrac{22}7[/tex], we have
[tex]\dfrac\ell{132\,\rm m}=\dfrac16\implies\ell=22\,\mathrm m[/tex]
so the answer is C.
