The disk for these exercises gives 5 years of monthly prices for two Vanguard funds—the Vanguard Index 500 fund (symbol VFINX) and the Vanguard High-Yield Corporate Bond fund (VWEHX). The first of these funds tracks the Standard and Poor’s 500, and VWEHX is a junk-bond fund. Compute the monthly returns and the frontier of combinations of these two funds.