A boy throws a ball into air at 45^° from the horizontal to land it on a roof of a building of height H. If the ball attains maximum height in 2 s…

A boy throws a ball into air at $\displaystyle 45^{\circ}$ from the horizontal to land it on a roof of a building of height $\displaystyle H$. If the ball attains maximum height in $\displaystyle 2$ s and lands on the building in $\displaystyle 3$ s after launch, then value of $\displaystyle H$ is $\displaystyle \_\_\_\_$ m. ( $\displaystyle \mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2$ )