Nvidia$$s market capitalization is $1\mathrm{.}80$ trillion dollars. It has $ $11$ billion debt outstanding. The $10-$year Treasury bond yield is $4\mathrm{.}5\%.$ Nvidia has an outstanding credit record and has earned an AAA rating from the major credit rating agencies. The current default premium on AAA corporate bonds is $1\%.$ The historical risk premium for stocks over the risk$-$free rate of return is $6$ percentage points. The firm$$s beta is estimated to be $1\mathrm{.}68$ and its marginal tax rate, including federal, state, and local taxes is $25\%.$

a$.$ What is the cost of equity?

b$.$ What is the after$-$tax cost of debt?

c$.$ What is the cost of capital?