A mild steel wire of length 2l metre cross-sectional area A my is fixed horizontally between two pillars. A small mass m kg is suspended from the mid point of the wire. If extension in wire are within elastic limit, then depression at the mid point of the wire will be
1. $(\frac{Mg}{YA})^{1/3}$
2. $(\frac{Mg}{lA})^{1/3}$
3. $(\frac{Mgl^3}{YA})^{1/3}$
4. None of these
