1. **State the problem:** A 60.0-kg boy runs up a flight of stairs 10.0 m high in 8.00 s. We need to find the minimum rate at which he uses energy, which is the power output. 2. **Formula used:** Power $P$ is the rate of doing work or using energy, given by $$P = \frac{W}{t}$$ where $W$ is work done and $t$ is time. 3. **Work done:** The work done to raise the boy to height $h$ against gravity is the change in gravitational potential energy: $$W = mgh$$ where $m = 60.0$ kg, $g = 9.8$ m/s$^2$, and $h = 10.0$ m. 4. **Calculate work done:** $$W = 60.0 \times 9.8 \times 10.0 = 5880 \text{ J}$$ 5. **Calculate power:** $$P = \frac{5880}{8.00} = 735 \text{ W}$$ 6. **Interpretation:** The minimum rate of energy use (power) is 735 W. **Final answer:** B) 735 W