This is equivalent to arithmetic progression a 1= 1269 1 in the first item, and d=-36.

an = a 1+(n- 1)d = 1269 1-(n- 1)* 36 = 12727-36d

/kloc-repayment in October/October is equivalent to an=8407 when n = 120, so the repayment in October 120 is 8407.

The total repayment amount is *** 120 months sn = na1+n (n-1) d/2 =1265880.