Mike is a self$-$employed computer game software designer. He takes a week$-$long trip to Maui, primarily for business. He takes $2$ personal days at the beach. How should he treat the expenses related to this trip?

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

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

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

d$.$ Fifty percent of the trip should be deducted as a business expense.