Exercise 31 Page 385

Before we are able to name a point that is coplanar with $D,$ $A,$ and $B,$ we first have to find the plane that contains these three points.

The points $D,$ $A,$ and $B$ are all on the top face of the cube. Extending the top face outwards in all directions will create the plane that contains $D,$ $A,$ and $B.$

The points $C$ and $I$ are also on the top face of the cube and are coplanar with $D,$ $A,$ and $B.$ Since we are to only name one such point, we will arbitrarily choose $C$ as our answer.