Lars, of mass 75.6 kg, has been working out and can do work for about 2.0 min at the rate of 0.980 hp (731 W). How long will it take him to climb three flights of stairs, a vertical height of 11.0 m?

Fl = mg = 75.6kg * 9.8N/KG = 740.88N =

Lars force.

P = F * d/t,
P = 740.88 * (11/t) = 731W,
8149.68 / t = 731,
t = 8149.68 / 731 = 11.15s.