companies issue bonds, preferred stock, and common equity to raise capital to invest in capital budgeting projects. capital is a necessary factor of production, and like any other factor, it has a cost. this cost is equal to the -select- required return on the applicable security. the rates of return that investors require on bonds, preferred stocks, and common equity represent the costs of those securities to the firm. companies estimate the required returns on their securities, calculate a weighted average of the costs of their different types of capital, and use this average cost for capital budgeting purposes.