1. The problem statement, all variables and given/known data A long conductive cylinder contains two cylindrical cavities, as shown in the diagram. Find the magnetic field produced at point P just above the surface of the cylinder, the total current in the I and uniform current density over its section. 2. Relevant equations Biot-Savart Ampere's law 3. The attempt at a solution I tried to use ampere's law, but I'm a bit confused what I should do. I don't know very well what i can do, if someone could help i appreciate.