A rod of mass $m$ and length $\boldsymbol{l}$ is attached to two ideal strings. Find tension in left string just after right string is cut.
(A) $\frac{2}{3}\mathrm{mg}$
(B) $\frac{\mathrm{mg}}{4}$
(C) $\frac{\mathrm{mg}}{5}$
(D) $\frac{\mathrm{mg}}{2}$