How can the angular momentum of a particle around a point be calculated using the vector between the point and the particle, $\vec{r}$, and the linear momentum vector, $\vec{p}$? What is the angular momentum of a particle of mass 3g at $\vec{r} = (1,2,0)$ cm with a linear velocity of $\vec{v} = (-1,1,0)$ cm s?¹?