45 degrees below the ground II

Classical Mechanics Level 1

A projectile is thrown horizontally from a $20\text{ m}$ building. If, at the landing point, the velocity vector of the projectile makes an angle of $45^\circ$ below the ground, calculate the projectile's initial speed in $\text{m/s}$ .

Take $g$ (the accelaration due to gravity) as $10 \text{ m/s}^2$ .