The answer is the first option. When Ricky sells his used desk for $50, money is a medium of exchange. As you can see, money permits that Ricky gets rid of his desk (because he prefers the $50 dollars, likely to perform other purcahse) while the purchaser of the desk prefers the used desk over the $50 (likely because he needed a desk and did not want to spend more than $50). In this way, the money permits that one purchases the product that he wanted (the used desk) and permits that Ricky has money to purchase othet object that he wants.
