A force of $50N$ is required to push a car on a level road with constant velocity of $10m/s$. The mass of the car is $500kg$. What force should be applied to make the car accelerate at $1m/s^2$?

I though that $F=ma=(500)(1)=500N$. But the answer happens to be 550N, also I don't know why the constant velocity was provided.