What are flotation costs and how do you incorporate them into the WACC calculation? Why is it important to consider flotation costs? Are the flotation costs different for the different capital components?

Do firms need to include the cost of common stock in the WACC if they plan to only use retained earnings and not issue any new shares? Are reinvested earnings "free"? What is the difference between the cost of common from reinvested earnings (internal equity) and the cost of common from external equity financing?