Exercise 39 Page 385

We want to use the given diagram to name all the points that are not coplanar with the given points. In this exercise the given points are $N,$ $K$ and $L.$ They are all on the top face of the cube. This means that the top face is contained within plane $NKL.$ Let's mark it on our diagram.

The plane $NKL$ is as if the top face was extended indefinitely in all directions. Even if we did so, there is no chance that the points not lying on the top face will be in that plane. Therefore, the points that are not coplanar with $N,$ $K,$ and $L$ are any points that are not on the top face of the cube. Let's mark them on our diagram.

The points that are not on the top face on the cube are $P,$ $Q,$ $R,$ and $S.$ These are the points which are not coplanar with the given ones.