Copper and aluminum are being considered for a high-voltage transmission line that must carry a current of 60.0 A. The resistance per unit length is to be 0.150Ω/km. The densities of copper and aluminum are 8960 and 2600 kg/m3, respectively. Compute

(a) The magnitude J of the current density and

(b) The mass per unit length), for a copper cable and

(c) J and

(d) λ for an aluminum cable.