Average atomic mass of magnesium is 24.31 amu. This magnesium is composed of 79 
mole % of  ${}^{24}\text{Mg}$ and remaining 21 mole of %   ${}^{25}\text{Mg}$ and  ${}^{26}\text{Mg}$. Calculate mole % of  ${}^{26}\text{Mg}$.