Question $3.$ Consider the adjusted closing prices of SP$500$ index, IBM stock, Apple Inc., and Johnson

& Johnson from Jan. $1,2000$ to September $8,2016.$

$($a$)$ Plot the time series of the adjusted closing prices of all four assets in a single pane. Label axes and

time series.

$($b$)$ Compare the distributions of the log$-$returns of all four assets using a side$-$by$-$side boxplot.

$($c$)$ Compute the summary statistics of the log$-$returns of all four assets using the function summary$().$

$($d$)$ Compute the IQRs and the standard deviations of the log$-$returns of all four assets. Rank the assets

according to their risk.