Tom invested $20,000 in a limited partnership. His share of liabilities from mortgage debt was initially $45,000. The property suffered a loss in income during the first year, of which Tom's share was $5,000. However, in years two through four income allocated from the account equaled a total of $9,000 ($3,000 per year). The reduction in debt at the end of year 4 from amortization of the loan is equal to $1,100. What is Tom's basis in the partnership interest at the end of year 4? (A) 17. (A) $67,900 (B)-$9,900 (C) 77,900 (D) $70,100