Melissa recently paid $400 for round-trip airfare to San Francisco to attend a business conference for three days. Melissa also paid the following expenses: $250 fee to register for the conference, $300 per night for three nights lodging, $200 for meals, and $150 for cab fare. (Leave no answers blank. Enter zero if applicable.) c. Suppose that Melissa made the trip to San Francisco primarily to visit the national parks and only attended the business conference as an incidental benefit of being present on the coast at that time. What amount of the airfare can Melissa deduct as a business expense?