[Assume that hydrolysis of ATP yields 12 kcal per mole. 1 watt = 1 joule/sec, 1 calorie = 4.18 joules, Avogadro's number = $6.023 \times 10^{23}$]
This problem requires calculating the total power utilized by the human body based on the given number of cells, ATP turnover rate per cell, and energy released per ATP molecule.
Total ATP turnover per minute is the product of the number of cells and the ATP turnover rate per cell.
Total ATP/min = Number of cells $\times$ ATP rate per cell
Total ATP/min = $(5 \times 10^{13} \text{ cells}) \times (10^9 \text{ ATP/cell/min})$
Total ATP/min = $5 \times 10^{22}$ ATP/min
Using Avogadro's number, we convert the number of ATP molecules to moles.
Total moles ATP/min = $\frac{\text{Total ATP/min}}{\text{Avogadro's number}}$
Total moles ATP/min = $\frac{5 \times 10^{22} \text{ ATP/min}}{6.023 \times 10^{23} \text{ ATP/mole}}$
Total moles ATP/min $\approx 0.08299$ moles/min
The total energy is the moles of ATP utilized multiplied by the energy yield per mole.
Energy (kcal/min) = Total moles ATP/min $\times$ Energy yield per mole
Energy (kcal/min) = $(0.08299 \text{ moles/min}) \times (12 \text{ kcal/mole})$
Energy (kcal/min) $\approx 0.9959$ kcal/min
We use the conversion factor 1 kcal = 1000 cal and 1 cal = 4.18 J.
Energy (J/min) = Energy (kcal/min) $\times 1000 \times 4.18$
Energy (J/min) = $(0.9959 \text{ kcal/min}) \times 1000 \times 4.18$
Energy (J/min) $\approx 4162.8$ J/min
Power is energy per unit time. 1 watt = 1 joule/sec.
Power (watts) = $\frac{\text{Energy (J/min)}}{60 \text{ sec/min}}$
Power (watts) = $\frac{4162.8 \text{ J/min}}{60 \text{ sec/min}}$
Power (watts) $\approx 69.38$ J/sec
The calculated power utilization is approximately 69.38 watts, rounded to two decimal places. This value falls within the expected range.