Explanation : Cost of capital means interest on debts or
dividend on shares. Debt is a cheaper source
of finance in comparison to equity capital
because rate of interest is lower than the return
expected by equity shareholders and the tax
deductibility of interest further reduces the
cost of debt. The preference share capital is
also cheaper than equity capital, but not as
cheap as debt. Thus, optimum capital structure
should include sufficient amount of debt since
it is the cheapest source of finance.