Define the term resistivity of conductor. Give its SI units. Show that the resistance of a conductor is given by
`R = (ml)/(ne^(2) tau A)`
where `tau` is average relaxation time.

Explanation

**Step-by-Step Solution:**

1. **Definition of Resistivity:**
Resistivity (ρ) is defined as the property of a material that quantifies how strongly it resists the flow of electric current. It is a measure of how much resistance a conductor offers per unit length and per unit cross-sectional area. Mathematically, resistivity is given by the formula:
\[ ρ = R \cdot \frac{A}{l} \]
where \( R \) is the resistance, \( A \) is the cross-sectional area, and \( l \) is the length of the conductor.
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