Pareto tail index for wealth above a threshold

Net worths above a known floor $x_m$ are modeled as Pareto with unknown index $\alpha$, density $f(x \mid \alpha) = \dfrac{\alpha x_m^{\alpha}}{x^{\alpha+1}}$ for $x \ge x_m$. A survey of $n = 80$ individuals has $\sum_i \ln(x_i / x_m) = 32$.

What is the maximum likelihood estimate of $\alpha$?