The first payment for a series of payments made at the end of each year for twenty years is now 1000 TL. In this series of payments, during the first ten years, each payment increases by 100 TL each year compared to the payment made in the previous year. In the second decade, 100 TL decreases every year compared to the previous year's payment. Calculate the cumulative value in the 21st year as the annual effective interest rate is 6%.

I need solution for my homework i have only 1 hour for this.I need step by step solution with formulas "not with excel report.or something like this" thanks.