$$A radioactive sample initially contains$0\mathrm{.}279$mol$$of radioactive nuclei whose half$-$life is$6\mathrm{.}00$h$6\mathrm{.}00$h$\mathrm{.}1)$How many moles of radioactive nuclei remain after$6\mathrm{.}00$h$6\mathrm{.}00$h$?2)$ How many moles of radioactive nuclei remain after $12\mathrm{.}0$ h$?$

$3)$ How many moles of radioactive nuclei remain after$42$hh$?$