Steel and copper wires of same length and area are stretched by the same weight one after the other. Young's modulus of steel and copper are $2\times {10}^{11} \mathrm{N}/{\mathrm{m}}^2$ and $1.2\times {10}^{11} \mathrm{N}/{\mathrm{m}}^2$. The ratio of increase in length is

• A

  $\frac{2}{5}$

• B

  $\frac{3}{5}$

• C

  $\frac{5}{4}$

• D

  $\frac{5}{2}$