calculate debt cost of capital if

rating at the end of $2017$ BB $2\mathrm{.}08\%$

risk free rate $0\mathrm{.}000561767$

cost of debt $2\mathrm{.}14\%$

tax rate $(2022.$Sep$)21\mathrm{.}60\%$

After$-$tax cost of debt $9\mathrm{.}89\%$