The articles of partnership for A-B partnership provide for a salary allowance of $5,000 per month for partner B, with the balance of net income to be divided equally. If B made an additional investment of $10,000 during the year and withdrew $4,000 per month, and net income for the year was $90,000, by what amount did B's capital increase during the year? A) $60,000 B) $37,000 C) $85,000