A \(20-\mathrm{kg}\) boy slides down a smooth, snow-covered hill on a plastic disk. The hill is at a \(10^{\circ}\) angle to the horizontal, and the slope is \(50 \mathrm{~m}\) long.

(a) If the boy starts from rest, what is his speed at the bottom of the hill?

(b) His sister then hauls him and the disk from the bottom to the top by means of a rope attached to the disk. What average force must she exert on the rope if the boy is going \(0.50 \mathrm{~m} / \mathrm{s}\) when he reaches the top?