A rubber catapult has a cross sectional area $2mm^2$ and total unstretched length 15cm.It is stretched to 18cm and then released to project a missile of 3g.Taking young modulus $8\times 10^8N/m^2$ find velocity of projection?

Question

$\begin{array}{1 1}(A)\;28m/s\\(B)\;56m/s\\(C)\;50m/s\\(D)\;\text{None of above}\end{array} $