Two bodies of 6 kg and 4 kg masses have their velocity $5 \hat i+ 2 \hat j +10 \hat k$ and $10 \hat i - 2 \hat j -8 \hat k$ respectively. Then the velocity of their center of mass is

Question

$$\begin {array} {1 1} (a)\;5 \hat i+ 2 \hat j-8 \hat k & \quad (b)\;7 \hat i+ 2 \hat j-8 \hat k \\ (c)\;7 \hat i - 2 \hat j + 8 \hat k & \quad (d)\;5 \hat i - 2 \hat j +8 \hat k \end {array}$$