What is the total pressure exerted by a mixture of $0\mathrm{.}45$ kg mole of benzene, $0\mathrm{.}44$ kg mole of toluene and $0\mathrm{.}23$ kg mole of o$-$xylene at $100$C$,$ if their vapor pressures at $100$C are $1340,560$ and $210$ mmHg respectively $?$

$756\mathrm{.}2$

$780\mathrm{.}5$

$801\mathrm{.}5$

$880\mathrm{.}5$