Answer:
Amortization table
Opening liability Installments Interest Principal payment Closing liability
139,108 18000 1211 16788.92498 122,319
122,319 18000 1043 16956.81423 105,362
105,362 18000 873 17126.38238 88,235
88,235 18000 702 17297.6462 70,938
70,938 18000 529 17470.62266 53,467
53,467 18000 354 17645.32889 35,822
35,822 18000 178 17821.78218 18,000
18,000 18000 0 0 0