\normalsize \begin{eqnarray} P(Y=1) &=& \ P(\mbox{first only or second only or third only or fourth only or fifth only} ) \\ \vspace{5} \\ &=& \ P(\mbox{first only} )+ P(\mbox{second only} )+P(\mbox{third only} )+P(\mbox{fourth only} )+P(\mbox{fifth only} ) \\ \vspace{5} \\ &\approx& \ 0.0167+0.0167+0.0167+0.0167+0.0167 \\ \vspace{5} \\ &=& \ (5)(0.0167) \\ \vspace{5} \\ &\approx& \ 0.0834 \end{eqnarray}