One problem with some of the newer high-temperature

Question

Solve the all parts of following question:

Question: One problem with some of the newer high-temperature superconductors is getting a large enough current density for practical use without causing the resistance to reappear. The maximum current density for which the material will remain a superconductor is called the critical current density of the material. In 1987, IBM research labs had produced thin films with critical current densities of 1.0 x 10⁵ A/cm².

Part A: How much current could an 18-gauge wire of this material carries and still remain superconducting? (18-gauge has a nominal diameter of 1.02 mm).

A

Part B: Researchers are trying to develop superconductors with critical current densities of 1.0 x 10⁶ A/cm². What diameter cylindrical wire of such a material would be needed to carry 956 A without losing its superconductivity?

mm

Please show your work, so I can understand process. Thanks!