Second month repayment10w+(2300-300-10) *1%= 29.9w.

Repayment in the third month10w+(2300-300-10 * 2) *1%= 29.8w.

……

Nth month repayment10w+[2300-300-10 * (n-1)] *1%.

Tenth month repayment10w+[2300-300-10 * (10-1)] *1%= 29.1w.

The full amount needs (2300-300)/ 10=200 months.

Actually gave 2300+(20+0.1) * 200/2 = 4310w.