2. Consider the points A(2,1,-1), B(3,0,2),C(4,-2,1) and D(5,-3,-2).
a) Determine whether the points A, B, C and D are coplanar.
b) Find the volume of a parallelepiped having $\overline{AB}$, $\overline{AC}$ and $\overline{AD}$ as adjacent edges.
c) Use a projection to find the height of the parallelepiped relative to the base containing the points A, B, C. Use a diagram to illustrate your construction.