Calculating Magnetic Field Due to Multiple Cavities Using Ampere's Law

[luiseduardo]

Homework Statement

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.

Homework Equations

Biot-Savart
Ampere's law

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.

 

[Simon Bridge]

Try to articulate the trouble you are having.

You know how to find B due to a current in the whole wire right?
I'm guessing the trouble is the holes - is that correct?
So apply the superposition principle.