$\phi$ is a linear fractional transformation such that $\phi(0) = 0, \phi(1) = 1$, and $\phi(2) = \infty$.
$\phi$ is a linear fractional transformation such that $\phi(0) = 0, \phi(1) = 1$, $\phi(2) = 2$, and $\phi(3) = \infty$.
I found this in a past final exam, so I don't have an answer for it.