Please give me your answer.

Q. Which of the following is correct about components of WACC?

1. There are no flotation costs associated with issuing new debt.
2. For mature companies, the book value weights of common stock and debt are very similar to the market value weights of common stock and debt.
3. All else being the same, higher corporate tax rate will result in lower WACC.
4. One cannot calculate WACC for a company that does not have debt.
5. The lower the proportion of debt in a firm's capital structure, the lower its WACC.