Find the mean for the set of grouped data.

$\backslash$table$[[$Interval$,$Frequency$],[0\mathrm{.}5-2\mathrm{.}5,1],[2\mathrm{.}5-4\mathrm{.}5,8],[4\mathrm{.}5-6\mathrm{.}5,4],[6\mathrm{.}5-8\mathrm{.}5,7]]$

The mean is $($Round to two decimal places if needed.$)$