The values of `xyz` is `15/2` or `18/5` according as the series `a, x, y, z, b` is an `AP` or `HP.` Find the values of `a & b` assuming them to be positive integer.

Explanation

To solve the problem, we need to find the values of \( a \) and \( b \) such that the series \( a, x, y, z, b \) is an arithmetic progression (AP) or a harmonic progression (HP) with the given conditions for \( xyz \).

### Step 1: Set up the equations for AP
In an arithmetic progression, the middle terms can be expressed in terms of the first and last terms. The common difference \( d \) can be defined as:
\[ d = \frac{b - a}{4} \]
The terms can be expressed as:
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