15. Refer to Figure 15-1. At an interest rate of 4 percent, how much is the excess money demand or supply? (2 marks) a) There is an excess money demand equal to the distance between a and b. b) There is an excess money demand equal to the distance between b and c. c) There is an excess money supply equal to the distance between b and a. d) There is an excess money supply equal to the distance between c and b