Chapter 1 - Section 1.3 - Early Definitions and Postulates - Exercises - Page 30: 38g

There is no plane determined by the points A, C, F, and H.

Using our tissue box visual from part (a); points A and C define one side of the tissue box (defined by rectangle ABCD) and points F and H would define the opposite/parallel side of the tissue box (rectangle EFGH).