Two particles of masses $2 \ kg$ and $1 \ kg$ are moving along the same line with speeds of $2 \ m/s$ and $5 \ m/s$ respectively. If both particles are moving in the same direction,the speed of the centre of mass is $v_1$. If both particles are moving in opposite directions,the speed of the centre of mass is $v_2$. Find $v_1$ and $v_2$.

• A
  $3 \ m/s, \ 1/3 \ m/s$
• B
  $1/3 \ m/s, \ 3 \ m/s$
• C
  $2 \ m/s, \ 1/2 \ m/s$
• D
  $1/2 \ m/s, \ 2 \ m/s$