Kimberly is a self-employed taxpayer. She recently spent $1,800 for airfare to travel to Italy. What amount of the airfare is deductible in each of the following alternative scenarios? (Leave no answers blank. Enter zero if applicable.)

a. Her trip was entirely for personal purposes.

b. On the trip, she spent seven days on personal activities and three days on business activities.

c. On the trip, she spent six days on business activities and four days on personal activities.

d. Her trip was entirely for business purposes.