Supraconductor

for C)... divide the b) by 2

remember that E=1/2.L.I² for b)

Flu > ev give you the answer d (just integrate what he wrote) now you have d) you have just to do answer c) = b) + d)

for a) please see this article : corollarytheorems . com / Design / inductor . htm We are looking for the magnetic field B... Think about where is the point P (inside or outside?) The formula is written, and is one of these. Be strong!