A velocity question.. Please give a thought :)?

A car goes down a road with velocity of 100m/s (this is only fictional). The driver fires a gun from the moving car in the same direction as the car is going. The muzzle velocity (speed at which the projectile leaves the muzzle of the gun) is 500m/s (also fictional). The question is: what is the velocity of the bullet to a hitchhiker who is standing a few miles away down the road? Air friction and force of gravity (which affect the bullet) are disregarded in this matter. Explain your answer please :) thank you!