\problemdata
{s01-ps10}
{random variable}
{Doritos}

\begin{problem}
Each bag of Doritos contains a cool
sticker.  There are $n$ different kinds of sticker, and I want to
collect at least one sticker of each kind.  (Assume that sticker kinds
in Dorito bags are uniformly random and mutually independent.)

\begin{problemparts}
\problempart Suppose that I have already collected $k$ kinds of
sticker.  What is the expected number of additional bags of Doritos
that I must eat to collect one additional kind of sticker?

\problempart What is the expected number of bags of Doritos that I
must eat to collect at least one sticker of each kind?

\end{problemparts}

\end{problem}
