Electric Circuit I

When a current of 5 A is passed through the parallel combination of an aluminum wire 7.5m long and copper wire 6m long, it is found that the current in the aluminum wire is 3A. The diameter of aluminum wire is 1 mm. Determine the diameter of copper wire. The resistivity of copper is 0.017 µΩ-m and that of aluminum is 0.028 µΩ-m.