To calculate John's hourly wage, we need to find out how many hours he works in a week.
John works 5 days a week and 8 hours each day:
\[ \text{Total hours per week} = 5 , \text{days} \times 8 , \text{hours/day} = 40 , \text{hours/week} \]
Now, we can find out how much he earns per hour by dividing his weekly earnings by the total hours he works:
\[ \text{Hourly wage} = \frac{\text{Weekly earnings}}{\text{Total hours}} = \frac{500.00}{40} = 12.50 \]
So, John earns $12.50 per hour.
The correct answer is C. 12.50.