Rank the following bonds in order from lowest credit risk to highest risk all with the same time to maturity, by their yield to maturity: (Rank: 1 = lowest, 4 = highest)

Treasury bond with yield of 4.95 percent = ?

United Airline bond with yield of 9.12 percent = ?

Bank of America bond with a yield of 6.83 percent = ?

Hewlett-Packard bond with yield of 6.30 percent = ?