Youre driving down a highway and you decide to accelerate

Question

Question:

You're driving down a highway, and you decide to accelerate flaunting the speed limit, you accelerate way up there. At one point, you're going (a) 100km/hr. Later, you're going (b) 0.25 times the speed of light.

For each case, how much is your car's length contracted, and how slow does time go for you? Your car is 15 feet long (4.5 meters), and take t₀ to be 1 second.