Equivalent resistance of another type.

A conducting medium is shaped in the form of a quarter of an annulus of radii $b$ and $a$ $(b > a)$ and thickness $t$ . The specific resistance of the medium is $\rho$ .

If the resistance between faces $LMNO$ and $PQRS$ is $\frac { A\rho }{ \pi t } \ln { \frac { b }{ a } },$ where $A$ is a positive integer, find $A$ .