The XYZ company is planning to put up its own building. Two proposals being considered are: a. The construction of the building now to cost P400,000. b. The construction of a smaller building now to cost P300,000 and at the end of 5 years, an extension to be added to cost P200,000. By how much is proposal B more economical than proposal A if interest rate is 20% and depreciation is to be neglected?