Calculate the present value of the following annuity streams: a. $7,000 received each year for four years on the last day of each year if your investments pay 6 percent compounded annually. b. $7,000 received each quarter for four years on the last day of each quarter if your investments pay 6 percent compounded quarterly. c. $7,000 received each year for four years on the first day of each year if your investments pay 6 percent compounded annually. d. $7,000 received each quarter for four years on the first day of each quarter if your investments pay 6 percent compounded quarterly?