Exercise for the Reader

Here's a question right off my graphics programming test today:

You have n (greater than 3) 3D points, each represented by three 32-bit floats. The first three points a, b, and c are guaranteed to not be colinear, but nothing else is guaranteed. Devise a strategy to store the set of points in minimal space (hint: use a plane defined by a, b, and c), and give how much space would be needed to store the n points.