… is on the plane … if

$\mathbf{P}=(x,y,z)$ is on the plane $ax+by+cz=5$ if $\mathbf{P}\cdot \mathbf{N}=|\mathbf{P}||\mathbf{N}|\cos \theta =5$. Since the largest value of $\cos \theta$ is 1, the smallest value of $|\mathbf{P}|$ is ______. This is the distance between ______.

Gilbert Strang, Calculus, 3rd edition (Wellesley-Cambridge Press; MIT OpenCourseWare RES.18-001) · §11.2 Planes and Projections, #29