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 \(10 \text{ m/s}^2\).