WACC$-$Market value weights The market values and after$-$tax costs of various sources of capital used by Ridge Tool are shown in the following table: Data table

$($Click on the icon here in order to copy the contents of the data table below

into a spreadsheet.$)$

a$.$ Calculate the firm's weighted average cost of capital.

b$.$ Explain how the firm can use this cost in the investment decision$-$making process.

a$.$ The firm's weighted average cost of capital, $r_a,$ using market value weights is $\%.($Round to two decimal places.$)$

Explain how the firm can use this cost in the investment decision$-$making process. $($Select the best answer below.$)$