A novel method of storing energy has been proposed. A huge underground superconducting coil, 1.00 km in

Question:

A novel method of storing energy has been proposed. A huge underground superconducting coil, 1.00 km in diameter, would be fabricated. It would carry a maximum current of 50.0 kA through each winding of a 150-turn Nb3Sn solenoid.
(a) If the inductance of this huge coil were 50.0 H, what would be the total energy stored?
(b) What would be the compressive force per meter length acting between two adjacent windings 0.250 m apart?