Bristol Car Service offers airport service in a mid-size city. Bristol charges $34 per trip to or from the airport. The variable cost for a trip totals $20, for fuel, driver, and so on. The monthly fixed cost for Bristol Rainbow Tours is $3,220. Required: a. How many trips must Bristol sell every month to break even? b. Bristol's owner believes that 240 trips is a reasonable forecast of the average monthly demand. What is the margin of safety in terms of the number of airport trips?