Answer
19 minutes.
Work Step by Step
If metabolism were to stop, heat loss would be by conduction and radiation, at a rate of 200 W. The change in temperature is related to the body’s heat loss by Eq. 14–2, $Q=mc\Delta T$.
$$\frac{Q}{t}=P=\frac{ mc\Delta T }{t}$$
$$t=\frac{ mc\Delta T }{P}=\frac{(65 kg)(3470J/(kg\cdot C))(1^{\circ})}{200W}=1128s\approx 19\;minutes$$
