An 80 kg astronaut has gone outside his space capsule to do some repair work. unfortunately, he forgot to lock his safety tether in place, and he has drifted 5.0 m away from the capsule. fortunately, he has a 1000 w portable laser with fresh batteries that will operate it for 1.0 h. his only chance is to accelerate himself toward the space capsule by firing the laser in the opposite direction. he has a 10-h supply of oxygen. how long it take him to reach safety?