ant to purc You are at a clothing store and have found a great shirt that you see a clerk who can take your payment. After waiting five minutes, you decide that you have had enough and are ready to leave without buying the shirt. But your friend says, "Since you've waited this long, you might as well keep waiting so the time you've spent doesn't go to waste." What kind of cost does the time you've already spent waiting represent? Select one: O a. fixed cost O b. marginal cost O c. variable cost O d. sunk cost