A 65-kg hiker climbs to the top of a 3700-m-high mountain. The climb is made in 5.0h

Question:

A 65-kg hiker climbs to the top of a 3700-m-high mountain. The climb is made in 5.0h starting at an elevation of 2300m. Calculate
(a) The work done by the hiker against gravity,
(b) The average power output in watts and in horsepower, and
(c) Assuming the body is 15% efficient, what rate of energy input was required.