Two bodies of masses $1 \mathrm{~kg}$ and $2 \mathrm{~kg}$ are connected by a metal wire shown in figure. A force of $10 \mathrm{~N}$ is applied on the body of mass $2 \mathrm{~kg}$. The breaking stress of metal wire is $2 \times 10^{9} \mathrm{~N} / \mathrm{m}^{2}$.
What should be minimum radius of the wire used, if it is not to break?
(a) $0.23 \times 10^{-4} \mathrm{~m}$
(b) $4 \times 10^{-1} \mathrm{~m}$
(c) $5 \times 10^{-4} \mathrm{~m}$
(d) $5.2 \times 10^{-i} \mathrm{~m}$