Answer
Please see the work below.
Work Step by Step
We know that if the speed of light were $3.5mi/h$ then we would have the following consequences.
1. The length of a car in motion would seem to be shorter because of length contraction.
2. A person in motion would age slowly as compared to a person who was at rest due to time dilation.
3. No object can move faster than light. Hence, even if the engine of your car is powerful, you would not be able to drive faster than $35mi/h$.
