Let $\alpha$ and $\beta$ be the roots of equation $px^2 + qx + r = 0,\; p \neq 0$. If $p, q, r$ are in A.P. and $\frac{1}{\alpha} + \frac{1}{\beta} = 4$, then the value of $|\alpha - \beta|$ is

Question

( A ) $\frac{\sqrt{34}}{9}$
( B ) $\frac{\sqrt{61}}{9}$
( C ) $\frac{2\sqrt{17}}{9}$
( D ) $\frac{2\sqrt{13}}{9}$