The barrel of a rifle has a length of 0.951 m. A bullet leaves the muzzle of a rifle with a speed of 563 m/s. What is the acceleration of the bullet

The barrel of a rifle has a length of 0.951 m. A bullet leaves the muzzle of a rifle with a speed of 563 m/s.

What is the acceleration of the bullet while in the barrel? A bullet in a rifle barrel does not have constant acceleration, but constant acceleration is to be assumed for this problem.

Answer in units of m/s^2.