On Thursday, Justin flies from Baltimore $($where the office for his sole proprietorship is located$)$ to Cadiz $($Spain$).$ He conducts business on Friday and Tuesday; vacations on Saturday, Sunday, and Monday $($a legal holiday in Spain$)$; and returns to Baltimore on Thursday. Justin is scheduled to return home on Wednesday, but all flights were canceled due to bad weather. As a result, he spends Wednesday watching floor shows at a local casino. Days where travel is attempted$/$canceled are counted as travel days under tax law. Justin is self$-$employed.

a$.$ For tax purposes, what portion of Justin's trip is regarded as being for business?

b$.$ Suppose Monday was not a legal holiday. Would this change your answer about what percentage of Justin's trip would be regarded as business?

c$.$ Under either part $($a$)$ or $($b$),$ how much of Justin's airfare qualifies as a deductible business expense?

Under part $($a$),($

Under part $($b$),$