        \problemdata       % Takes 5 *mandatory* arguments
        {variance-6}             % latex-friendly label for the prob.
        {variance}               % The topic of the problem content.
        {Velleman}               % Source (if known)
        {S98 PS11-7; F97 PS11-8} % Usage (list ones you are aware of).
        {Theory Pig, S02}        % Last revision info (author, date).
\begin{problem}
Let $R:S\rightarrow \naturals$ be a random variable.
\begin{problemparts}
\problempart
Let $R'=cR$ for some positive constant~$c$.
If $\sigma_R = s$, what is $\sigma_{R'}$?
\problempart
If $\expect{R}=1$, how large can $\variance{R}$ be?
\problempart
If $R$ is always positive (nonzero), how large can $\expect{1/R}$ be?
\end{problemparts}
\end{problem}
