A conducting disk with radius a, thickness h, and resistivity is inside a solenoid of circular

Question:

A conducting disk with radius a, thickness h, and resistivity ρ is inside a solenoid of circular cross section, its axis coinciding with the solenoid axis. The magnetic field in the solenoid is given by B = bt, where b is a constant. Find expressions for
(a) the current density in the disk as a function of the distance r from the disk center and
(b) the power dissipation in the entire disk.