Chris Mack, a local CPA, is a self-employed tax return preparer. Chris works from home in a room that is exclusively used on a regular basis as the principal place of business. Last year, Chris built a new bathroom across the hall for his clients' use. Although the vast majority of use of the bathroom is from clients, occasionally a family member or guest uses the bathroom. Can Chris deduct the additional bathroom space as part of his home office?

Provide the appropriate Internal Revenue Code for this question.