Projectile Angular Momentum

A particle of mass 100g is projected at time t=0 with a speed 20ms−1 at an angle 45∘ to the horizontal as given in the figure. The magnitude of the angular momentum of the particle about the starting point at time t=2s is found to be √K‌kg‌m2∕ s. The value of K is ________.
(. Take g=10ms−2)