A copper wire of length \(2.4 \mathrm{~m}\) and an aluminum wire of length \(0.7 \mathrm{~m}\), both having diameter \(2 \mathrm{~mm}\), are connected end to end. When stretched by a load, the obtained elongation is found to be \(0.6 \mathrm{~mm}\).The applied load is (Young's modulus of copper \(=1.2 \times 10^{11} \mathrm{Nm}^{-2}\) and Young's modulus of aluminum \(=0.7 \times 10^{11} \mathrm{Nm}^{-2}\) )

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.