Suppose that the current density in a wire of radius a varius with r according to `Kr^2` where K is a constant and r is the distance from the axis of the wire. Find the magnetic field at a point at distance r form the axis when (a) r`lt`a and (b) r`gt`a.

Explanation

To solve the problem of finding the magnetic field at a distance \( r \) from the axis of a wire with a varying current density \( J = Kr^2 \), we will analyze two cases: (a) when \( r < a \) and (b) when \( r > a \).

### Step-by-Step Solution

**Given:**
- Current density \( J = Kr^2 \)
- Radius of the wire \( a \)

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