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$)$

$\backslash$table$[[,],[$Treasury bond with yield of $4\mathrm{.}80$ percent,$],[$United Airline bond with yield of $9\mathrm{.}22$ percent,$],[$Bank of America bond with a yield of $6\mathrm{.}40$ percent,$],[$Hewlett$-$Packard bond with yield of $6\mathrm{.}93$ percent,$]]$