A particle attached to an ideal string is projected from position B (lowest position). At position A, tension in string becomes zero. Find speed in string at B.\\
(A) $\sqrt { 5 \mathrm { gl } }$\\
(B) $\sqrt { \frac { 7 \mathrm { gl } } { 2 } }$\\
(C) $\sqrt { \frac { 3 \mathrm { gl } } { 2 } }$\\
(D) $\sqrt { 2 \mathrm { gl } }$