Two particles of mass 1 kg and 3 kg have position vectors $ 2 \overrightarrow i + 3\overrightarrow j+4\overrightarrow k \: and \: -2\overrightarrow i+3\overrightarrow j-4\overrightarrow k$ respectively. The position vector of centre of mass of the system is

Question

$\begin {array} {1 1} (1)\;- \overrightarrow i +3\overrightarrow j -2\overrightarrow k & \quad (2)\;- \overrightarrow i +3\overrightarrow j+2\overrightarrow k \\ (3)\;- \overrightarrow i -3\overrightarrow j -2\overrightarrow k & \quad (4)\;\overrightarrow i +3\overrightarrow j-2\overrightarrow k \end {array}$