Andrew's principle place of business in the home office. Andrew may deduct expenses related to the to the use of his home office only if which of the following is true?

a it is accessible to the public through a seperste entrance

b the office contributes substantially of the profitability of his business

c the office is used exclusively and regularly for purposes related the Andrew's business

d the use of a separate office must be a generally accepted practice in Andrew's field of business