Answer
$2.06 \times 10^4 J$.
Work Step by Step
The firefighter exerts an upward force equal to his weight. The force and the displacement are both straight upward. The angle between them is 0 degrees. Use equation 6–1.
$$W=(75.0 kg)(9.80 \frac{m}{s^2})(28.0 m)(cos 0^{\circ})=2.06 \times 10^4 J$$
