Joe is a self$-$employed information technology consultant from San Francisco. He takes a week$-$long trip to Chicago primarily for business. He takes $2$ personal days to go to museums and see the sights of Chicago. How should he treat the expenses related to this trip?

a$.$ The cost of all of the airfare and the business days should be deducted, while the cost of the personal days are not deductible.

b$.$ Half of the trip should be deducted as a business expense since the IRS limits such business expenses to $50$ percent of the actual cost.

c$.$ One hundred percent of the trip should be deducted as a business expense since the trip was primarily for business.

d$.$ None of the expenses are deductible since there was an element of personal enjoyment in the trip.