Charles is a self employed CPA who maintains a qualifying office in his home. Charles has​ $110,000 gross income from his practice and incurs​ $88,000 in​ salaries, supplies, computer​ services, etc.​ Charles's mortgage interest and real estate taxes allocable to the office total​ $10,000. Other expenses total​ $14,000 and consist of​ depreciation, utilities,​ insurance, and maintenance. What is​ Charles' total home office expense​ deduction?