Question: The website ultrinsic.com has developed an "ulterior motive that causes the person to have an intrinsic love of knowledge." At Ultrinsic, students pay a small entry fee to compete in grades-based contests for cash prizes. Suppose that 20 students from your economics class each pay $20 to enter a grades-based contest. This would create a $400 prize pool. An equal share of the $400 pot is awarded at the end of the term to each contestant who earns an A in the course. If four students earn A's, they each receive $100. If only one student earns an A, that person gets the entire $400 pot. What economic concept is Ultrinsic harnessing in order to encourage participants to learn more?