[math] \newcommand{\NA}{{\rm NA}} \newcommand{\mat}[1]{{\bf#1}} \newcommand{\exref}[1]{\ref{##1}} \newcommand{\secstoprocess}{\all} \newcommand{\NA}{{\rm NA}} \newcommand{\mathds}{\mathbb}[/math]

A certain state has license plates showing three numbers and

three letters. How many different license plates are possible

• if the numbers must come before the letters?
• if there is no restriction on where the letters and numbers appear?