a survey of people on pizza preferences indicated that 55 percent preferred pepperoni only, 30 percent preferred mushroom only, and 15 percent preferred something other than pepperoni and mushroom. suppose one person who was surveyed will be selected at random. let p represent the event that the selected person preferred pepperoni, and let m represent the event that the selected person preferred mushroom. are p and m mutually exclusive events for the people in this survey?