Rock climber question?

Question

A rock climber of mass 70.0 kg wears a 12.0 kg knapsack while scaling a cliff. After 30.0 minutes, the climber is 8.20 m above the starting point.
(i) During the 30.0 min climb, what is the climber's average power in kilowatts?
(ii) If the climber drops the knapsack from 8.2 m, determine the velocity of the knapsack at the instant before it strikes the ground at the climber's starting point

Answer 1

∆PE = mgh = 82*9.81*8.2 = 6,596.244 J
P = 6,596.244 J / (30*60) = 3.66458 watts

12*9.81*8.2 = (1/2)(12)v^2
v^2 = 2*9.81*8.2 = 160.884
v = 12.684 m/s