In a fractional-reserve banking system with no excess reserves and no currency holdings, if the central bank buys $100 million worth of bonds, a. both reserves and the money supply increase by more than $100 million. b. reserves increase by $100 million and the money supply increases by $100 million. c. reserves increase by $100 million and the money supply increases by more than $100 million. d. reserves and the money supply increase by less than $100 million.