[tex]\boxed{\begin{array}{l}\tt a)~\sf\underbrace{\sf CONTAGEM}_{ P_8}=8!=40320\\\tt b)~\sf\underline{8}\cdot\underline{7}\cdot\underline{6}\cdot\underline{5}\cdot\underline{4}=6720\\\tt e)~\sf\underline{1}\cdot\underline{7}\cdot\underline{6}\cdot\underline{5}\cdot\underline{4}=840\end{array}}[/tex]
