Rational Numbers — Definition & Examples

A switchboard assigns the value $1$ to a number that's rational and $0$ to a number that's irrational. $$\begin{array}{c|c} \text{A}&\text{B}\\ \hline \frac{4\pi}{3\pi}&\frac{\pi}2 \end{array}$$ What would the switchboard say about the output of $A$ and $B$?