Decaborane, $B_{10}{H}_{14},$ was used as a fuel for rockets in the $1950$s: It reacts violently with oxygen, $O_2,$ to produce $B_2{O}_3$ and water. Calculate the percentage by mass of $B_{10}{H}_{14}$ in a fuel mixture designed to ensure that $B_{10}{H}_{14}$ and $O_2$ run out at exactly the same time. $($Such a mixture minimizes the mass of fuel that a rocket must carry.$)$