<prompt> Human: It begins March 2015 when I borrowed 7 000 from my brother to pay for a course i was doing. As a student I wasnt working very well to pay off the debt but I would pay some chunks whenever I could. Here is the list of all the payments i made to date. 2 apr 15 80022 may 15 50018 jun 15 7003 sept 15 70012 sept 15 60023 oct 15 5003 dec 15 70031 dec 15 100025 feb 16 3004 jun 16 200020 jun 16 10005 aug 16 50012 aug 16 100026 aug 16 1000Somewhere around November 2015 my brother wouldnt stop talking about the amount of debt he is facing on his 13.49 p.a credit card that he used to pay for my course. Oh by the way: he made some personal purchases using the same credit card but he hasnt specified how much. The total amount of debt was up to 19 000.According to my calculations i paid 11 300 to date and he expects me to pay another 5 500 to clear my part of the debt. Making it a total of will make it a total of 9800 in accrued interest in 17 months. Is that logical?  <response>: No, not at all.Youre getting fucked son.If you ignore all your payments in the first year, youre paying 13.5 interest 945 of interest after the first year. Since youve paid a lot of capital too two months already exceeds all interest, it will be lower than this.Your brother is either lying about his APR, or hes FLEECING you for his personal purchases.Ive knocked up a shitty example in Excel which is not representative as your payment date massively varies, but youve overpaid by at least 3815 I reckon. 