What is the difficulty in determine the optimal capital structure? a. There exists a singular optimal capital structure-if you look hard enough. If at first you don't suceeed try, try again. b. It isn't difficult. c. There are feedback loops between the cost of debt, cost of equity, and the percentage of debt and equity-so there is no necessary optimal solution. d. The optimal capital structure is one in which the future expectations of firm investment are taken into account in determining how much capital is needed from which source and this flows through to the costs of those capitals. Finding the minimum cost structure under this framework is the optimal capital structure