Answer:
c. 56.2 mph
Explanation:
In most cars, the speedometer reading is proportional to tire rotation speed, so a larger diameter tire will go farther for the same number of rotations. That is, the distance traveled in a certain length of time is proportional to the tire circumference, which is proportional to the tire diameter.
The car with new tires will actually be going at the speed of ...
(26 in)/(24.5 in) × (53 mi/h) ≈ 56.245 mi/h ≈ 56.2 mph