<<echo=FALSE, results=hide>>=
cf0 <- sample(10:16, 1) * -100
ocf <- sample(seq(225, 550, 25), 5)

npvfunc <- function(r) {
  discounts <- sapply(1:5, function(i) (1 + r) ** i)
  npv <- (sum(ocf / discounts) + cf0) ** 2
  return(npv)
}

res <- optimize(npvfunc, interval = c(-1,1))

irr <- round(res$minimum, 4) * 100.0

wrong1 <- irr + sample(c(1.0, -1.0), 1)
wrong2 <- irr + sample(c(0.25, -0.25), 1)
wrong3 <- irr + sample(c(0.5, -0.5), 1)
wrong4 <- irr + sample(c(0.75, -0.75), 1)
@

\begin{question}
Find the internal rate of return of a project with the following cash flows,
starting at time 0: \$\Sexpr{cf0}, \Sexpr{ocf[1]}, \Sexpr{ocf[2]}, 
\Sexpr{ocf[3]}, \Sexpr{ocf[4]}, \Sexpr{ocf[5]}.
\begin{answerlist}
  \item \Sexpr{wrong1}\%
  \item \Sexpr{wrong2}\%
  \item \Sexpr{irr}\%
  \item \Sexpr{wrong3}\%
  \item \Sexpr{wrong4}\%
\end{answerlist}
\end{question}

\exname{Calculating IRR}
\extype{schoice}
\exsolution{00100}
\exshuffle{5}