calculus and representation of magnetic field produced by a known distribution of current

Question

I must choose a distribution of electric current to calculate more easily magnetic field (for example using Ampere theorem) and to describe the distribution of current pick and say how to calculate the magnetic field. (also to represent the magnetic field) 

How I must start to do that? Any help will be very well receive. Thanks in advance.

Comments

Voting to close as low-level.