Isaiah is a self-employed therapist who operates a qualifying office in his home. Isaiah has $100,000 gross income from his practice and $80,000 of expenses directly related to the business, i.e., non-home office expenses. Isaiah's allocable home office expenses for mortgage interest expenses and property taxes are $12,000 and other home office expenses are $10,000. What is Alex's total allowable home office deduction?

A) $10,000

B) $12,000

C) $20,000

D) $22,000