How much would you have to invest today to receive the following? (Enter all answers as positive numbers.) a. $13,600 in 11 years at 8 percent. (Round your answer to 2 decimal places.) b. $17,500 in 17 years at 13 percent. (Round your answer to 2 decimal places.) c. $7,000 each year for 20 years at 8 percent. (Round your answer to 2 decimal places.)