A rifle has a m of 4.5 kg and it fires a bullet of m 10.0 g at a muzzle speed of 820 m/s...?

A rifle has a m of 4.5 kg and it fires a bullet of m 10.0 g at a muzzle speed of 820 m/s. What is the recoil speed of the rifle as the bullet leaves the gun barrel (m/s)?