How was this plotted?

b) Now suppose Exxon Mobil, an AAA-rated company, had bonds with the same maturities as the Treasury bonds.As an approximation, plot an Exxon Mobil yield curve on the same graph with the Treasury bond yield curve.(Hint: Think about the default risk premium on ExxonMobil's long-term versus its short-term bonds.)

c) Now plot the approximate yield curve of Exelon Corp., a risky nuclear utility.