Using the following partial table of present value of $1 at compound interest, determine the present value of $20,000 to be received four years hence with earnings at the rate of 12% a year: Year 6% 10% 12% 1 .943 .909 .893 2 .890 .826 .797 3 .840 .751 .712 4 .792 .683 .636 a. $13,660 b. $12,720 c. $15,840 d. $10,400