4.3. There are four non-coplanar points. How many planes are equally distant from these four points?
4.3. All 4 points cannot be on the same side of a plane, as they would otherwise be coplanar. Thus, we distinguish two cases. In the first case, three points are located on one side of the plane, and the fourth is on the other side. There are four such planes. In the second case, two points are located on different sides of the plane. The selection of a pair of points then uniquely determines the plane. It represents the perpendicular bisector of the common normal of the skew lines determined by the corresponding pairs of points. In this case, we have three planes. In total, therefore, seven.