From your statement, i can assume that the interest 6.5% is for yearly.
30 months = 2.5 years
1 year interest for 100 = 6.5
1 year interest for 12000 = 6.5/100 * 12000
= 780
2.5 years interest for 12000 = 780*2.5
= 1950
so the total amount that you have to pay
12000 + 1950
$ 13950
