The resultant of two vectors $\overrightarrow{\mathrm{A}}=5\widehat{\mathrm{i}}$ and $\overrightarrow{\mathrm{B}}\text{ is }\overrightarrow{\mathrm{R}}$. The direction of $\overrightarrow{\mathrm{R}}$ is such that it makes an angle $\frac{\mathrm{\pi }}{6}$ with the positive x - axis in anticlockwise sence. Find the magnitude of $\overrightarrow{\mathrm{R}}$(in cm) when $\overrightarrow{\mathrm{B}}$ has minimum magnitude.( Take $\sqrt{3}=1.732$ )