Question 7A tetrahedron in $\mathbb R^3$ has one vertex at the origin $O$ and the other vertices at the points $A(6,0,0)$, $B(4,2,4)$ and $C(3,2,6)$. If $x$ is the height of the tetrahedron from $O$ to the plane $ABC$, find $\lfloor5x^2\rfloor$.