AAA bonds carry compensation for default risk of $1\mathrm{.}5\%$ compared to T$-$bonds

Weaker secondary market $($usually for corporate bonds$)$ activity requires $1\%$ extra

return

The differential in default risk premium between the AAA and the BBB bonds is

$0\mathrm{.}3\%.$

Assume that there are no "other" factors contributing to the ROR.

Inflation expectations are flat between the time period of $10-15$ years.

The MRP does not increase beyond the $10-$year maturity.

$*$MRP stands for maturity risk premium.