A researcher must estimate how many packs of disinfecting wipes will be purchased by businesses in Cleveland, Ohio for the annual sales forecast. Her plan is to ask managers the likelihood that they will purchase disinfecting wipes, and she will ask those who say they are “very likely” to purchase them to estimate how many packs (each with 100 wipes) their company will buy. She can divide the companies into small, medium, and large firms based on number of employees at their Cleveland offices. a. What sampling plan should be used? b. Why?