The velocities of three particles of masses $20\; g, \; 30\; g$ and $50\; g$ are $10 \hat{i}, \; 10 \hat{j}$ and $10 \hat{k}$ respectively. The velocity of the centre of mass of the three particles is :

Question

( A ) $2 \hat{i} + 30 \hat{j} + 50 \hat{k}$
( B ) $10(\hat{i} + \hat{j} + \hat{k})$
( C ) $20 \hat{i} + 30 \hat{j} + 50 \hat{k}$
( D ) $2 \hat{i} + 3 \hat{j} + 5 \hat{k}$