A bullet of mAS 0.02 kg is fired from a gun of mass 100 kg, if the muzzle speed of the bullet is 80m/s, what is the recoil speed of the gun?

plz answer this

MASS OF BULLET+GUN = 0.02KG
INITIAL VELOCITY OF BULLET+GUN = 0
INITIAL MOMENTUM OF BULLET=M.V = 0(VELOCITY = 0)........(1)
NOW, FINAL VELOCITY OF BULLET = 80M/S
FINAL MOMENTUM OF BULLET=M.V = 0.02.80=1.6
FINAL VELOCITY OF BULLET=V
FINAL MOMENTUM OF BULLET=100.V
SINCE THEIR IS NO EXTERNAL FORCE,
100V+1.6=0
V = 1.6 . 10-2M/S

REGARDS.
HARDIK BAWEJA