## Calculus (3rd Edition)

$$\sqrt{26}.$$
First, we have $$\overrightarrow{ OR}=R-O=(1,4,3)-(0,0,0)=\langle 1,4,3 \rangle.$$ Now, $$\|\overrightarrow{ OR}\|=\sqrt{1+16+9}=\sqrt{26}.$$