To find the mileage per gallon for Mr. Gladden, you can use the formula:
\[ \text{Mileage (mpg)} = \frac{\text{Total miles driven}}{\text{Total gallons of gas used}} \]
Plugging in the given values:
\[ \text{Mileage} = \frac{548 \text{ miles}}{15.22 \text{ gallons}} \approx 36.01 \text{ mpg} \]
Therefore, the correct response is 36.01 mpg.