On 1/1/2018, A and B as equal partners form partnership AB. Both A and B, as well as partnership AB, are calendar year taxpayers. On 1/1/2018, A and B each contributes $10,000 from personal assets to AB. On 8/1/2018, AB borrows $5,000 from a bank with A and B each assuming personal liability. On 12/1/2018, AB reduces the amount outstanding on the loan to $4,000. AB has neither loss nor income for 2018.

 Compute A's amount at risk (AAR) as of 12/31/2018.