Answer
$P = 463~watts$
Work Step by Step
The work $W$ that the firefighter does is equal to the change in potential energy.
$W = PE$
$W = mgh$
$W = (90~kg+40~kg)(9.80~m/s^2)(20~m)$
$W = 25,480~J$
We can find the required power as;
$P = \frac{Work}{time}$
$P = \frac{25,480~J}{55~s}$
$P = 463~watts$
