\(L=\vec{r} \times m \vec{v}\)

\(L=m v r_\perp\)

\(L=m v H \cos \theta\) \(........(I)\)

The formula for maximum height during projectile motion is,

\(h=\frac{(v \sin \theta)^{2}}{2 g}\)

Substitute the expression in equation \((I).\)

\(L=\frac{(v \sin \theta)^{2}}{2 g} \times m v \cos \theta\)

\(L=\frac{10^{2} \sin ^{2} 60}{2 \times 10} \times 0.16 \times 10 \cos 60^{\circ}\)

\(=3 kgm ^{2} / s\)