An astronaut of 51 kg is in space, far from any objects which would apply a significant gravitational force on him. He would like to move in the direction of his spaceship; however his jet pack is not working. He throws a 720 g socket wrench having a velocity of 5 m/s in a direction away from the ship. After 0.50 s, he throws an 800 g spanner in the similar direction having a speed of 8 m/s. After the other 9.90 s, he throws a mallet having a speed of 6 m/s in the similar direction. The mallet consists of a mass of 1050 g. Determine how fast is the astronaut moving after he throws the mallet?