Hydrogen iodide gas decomposes at $410$C:

$2$HI$($g$)->$H$2($g$)+$I$2($g$)$

The following data describe this decomposition:

Time $($min$)020406080$

$[$HI$]0\mathrm{.}5000\mathrm{.}3820\mathrm{.}3100\mathrm{.}2600\mathrm{.}224$At what time $($in minutes$)$ does the HI concentration reach $0\mathrm{.}180$ M $?$