copper wire and an aluminium wire have lengths in the ratio 3 : 2, diameters in the ratio 2 : 3 and forces applied in the ratio 4 : 5. Find the ratio of the increase in length of the two wires. $\left({\mathrm{Y}}_{\mathrm{Cu}}=1.1\times {10}^{11} {\mathrm{Nm}}^2, {\mathrm{Y}}_{\mathrm{Al}}=0.70\times {10}^{11} {\mathrm{Nm}}^{-2}\right)$