Accounts Receivable balance: don't see my mistake, I get wrong answer

Hello!

It seems to be a pretty easy task, but I don’t understand why I get the wrong answer. The answer from the book is AR = 16 465, but I get a different number. Here is the task (I uploaded it to the google drive as a screen shot):

description of the task My computations:

Debit Accounts Receivable: Oct.7 6,900 Oct. 12 900 Oct. 15 460 (it is said that this was added to customer balances as finance charges) Oct. 24 9000 (as the note receivable is dishonored, the amount is transferred to AR account) Oct. 24 51 (9000 * 7% * (29 days / 360 days) = 51 interest on the dishonored note) ________ 17 311 Please, help me to find my mistake. Thank you very much!