Solve the Problem $21 \mathrm{mpg}$ on a Smooth Road, Its Mileage Is

Solve the problem.
-The normal gasoline mileage of a car is $21 \mathrm{mpg}$ . On a smooth road, its mileage is $12 \%$ higher. What is its mileage on a smooth road? Round your answer to the nearest tenth.

A) $50 \mathrm{mpg}$
B) $21 \mathrm{mpg}$
C) $2.5 \mathrm{mpg}$
D) $23.5 \mathrm{mpg}$