Question

a 123 kg man space finds himself 60 m away from his space ship and wants to get back. he holds a 2kg space gun which fires 5.00g bullet at a rate of 1500m/s. if he fires a single bullet in a direction directly away from the spaceship, how long would it take the man to arrive back to his ship in.

recoil of gun is 0=2vg +.005*1500
vg=-3.75

please help. i just don't know where to go after i get the recoil of gun