$[$Gumbel method$]$

In one study, an $8-$year rainfall record was collected at rainfall increments of $10$ minutes.

The top $5$ annual maximum rainfall increments are listed below:

Rank $12345$

$10-$min rainfall $($mm$)39\mathrm{.}639\mathrm{.}438\mathrm{.}537\mathrm{.}336\mathrm{.}5$

Estimate the frequency distribution of the annual maxima with return periods greater than $2$

years.