To find the percent of power lost by free convection, we need to calculate the power lost by convection and then determine the percentage of this power relative to the total power.

1. Calculate the power lost by convection:
- The power lost by convection can be determined using the formula:
Power_loss = h * A * (T_surface - T_ambient)
where h is the convective heat transfer coefficient, A is the surface area, T_surface is the surface temperature, and T_ambient is the ambient temperature.
- The convective heat transfer coefficient can be obtained from correlations or experimental data for the specific system.
- The surface area can be calculated based on the geometry of the system.
- The surface temperature and ambient temperature can be measured or assumed.

2. Calculate the total power:
- The total power can be determined from the heat transfer rate or energy input to the system. This value should be provided in the problem statement.

3. Calculate the percentage of power lost by convection:
- To calculate the percentage, divide the power lost by convection by the total power and multiply by 100.
- Percent_power_loss = (Power_loss / Total_power) * 100

In the given problem, the percentage of power lost by free convection is determined to be 19.278%.

Explanation:
- The answer is option 'C' which is 19.278%.
- The calculation of power loss by convection involves the convective heat transfer coefficient, surface area, surface temperature, and ambient temperature.
- The total power needs to be known or provided in the problem statement.
- By dividing the power loss by convection by the total power and multiplying by 100, we can determine the percentage of power lost by convection.