A parallelogram has sides $30 m, 70 m$ and one of its diagonals is $80 m$ long. Its area will be
$600\displaystyle m^{2}$
$\displaystyle 1200\sqrt{3}m^{2}$
$1200\displaystyle m^{2}$
$\displaystyle 600\sqrt{3} m^{2}$