An explosion breaks a rock into three parts in a horizontal plane. Twoof themgooff at right angles to each other. Thefirst part of mass 1 kg moves with a speed of 12 $$ms^{-1}$$ and the secondpart of mass 2 kgmoves with 8 $$ms^{-1}$$ speed. If the thirdpart flies off with 4 $$ms^{-1}$$ speed, then its mass is :

A

17kg

B

3 kg

C

5 kg

D

7 kg