1. The problem statement, all variables and given/known data Please find it attached. 2. Relevant equations 3. The attempt at a solution Ok so at point P the net magnetic field strength is zero, thus if I were to equate the magnetic fields at point P due to the cylinder, and then due to the wire, and sum them together using the principle of superposition and set that result equal to zero solving that for the current on the wire yields the answer tothe first part. Now from the biot savart law I get the magnetic field due to the current on the wire as being : But I'm not sure on how to do the same for the cylinder, any hints?