A gearset has a diametral pitch of 5 teeth/in, a 20 pressure angle, and a 24-tooth cast-iron

Question:

A gearset has a diametral pitch of 5 teeth/in, a 20◦ pressure angle, and a 24-tooth cast-iron spur pinion driving a 48-tooth cast-iron gear. The pinion is to rotate at 50 rev/min. What horsepower input can be used with this gearset if the contact stress is limited to 100 kpsi and F = 2.5 in?