Two bodies of masses `10 kg and 2 kg` are moving with velocities `(2 hati - 7 hatj + 3hat k) and (-10 hati + 35 hatj - 3hatk) m//s` respectively. Calculate the velocity of their centre of mass.
A. `2hati m s^(-1)`
B. `2 hatk m s^(-1)`
C. `(2hatj+2hatk) m s^(-1)`
D. `(2hati+2hatj+2hatk) m s^(-1)`
