The Young’s modulus of a steel wire of length 6 m and cross-sectional area $3 {\mathrm{mm}}^2$, is$2\times {10}^{11} \mathrm{N}/{\mathrm{m}}^2$ . The wire is suspended from its support on a given planet. A block of mass $4 \mathrm{kg}$ is attached to the free end of the wire. The acceleration due to gravity on the planet is $\frac{1}{4}$ of its value on the earth. The elongation of wire is (Take g on the earth = 10 m/s²)