A shift in demand is defined as a change in the quantity demanded at any price. Which of the following situations best exemplifies a shift in demand? Group of answer choices An advertising campaign increases public awareness of a new product A manufacturer publishes a coupon for 50 cents off of their product A shortage of a key input temporarily reduces the availability of a product A firm that uses petroleum as a key input in their manufacturing process has to increase their product price as the price of oil risesWhy should economists and managers care about elasticity? Group of answer choices Elasticity keeps our underwear from falling down Elasticity tells us the optimal price we should charge for our products Elasticity tells us about how changes in price can be expected to change revenue Elasticity tells us about the slope of our demand curve