\begin{tcolorbox}[colback=white, colframe=black, colbacktitle=white, coltitle=black, title=QuickTip, width=\textwidth, halign=left] For problems involving arrangements of letters, use the formula for permutations with repetition and arrange the letters in lexicographical order. \end{tcolorbox} \vspace{0.5cm} \hline \vspace{0.5cm}