A uniform disk of mass $10.0 \mathrm{kg}$ and radius $0.250 \mathrm{m}$ spins at 300 rev/min on a low-friction axle. It must be brought to a stop in 1.00 min by a brake pad that makes contact with the disk at an average distance $0.220 \mathrm{m}$ from the axis. The coefficient of friction between pad and disk is $0.500 .$ A piston in a cylinder of diameter $5.00 \mathrm{cm}$ presses the brake pad against the disk. Find the pressure required for the brake fluid in the cylinder.