6. Which of the following is correct about the effective-interest method of amortization?

a. The effective interest method applied to investments in debt securities is different from that applied to bonds payable. b. Amortization of a discount decreases from period to period. c. Amortization of a premium decreases from period to period. d. The effective-interest method produces a constant rate of return on the book value of the investment from period to period.