A stone is dropped from the top of a tower of height $h\mathit{.}\mathit{ }n$ seconds later, a second stone is thrown downwards from the same point with a vertically downward velocity $u$. Show that the two stones will reach the foot of the tower simultaneously if $8h{\left(u-gn\right)}^2=g{n}^2{\left(2u-gn\right)}^2$.