if possible solve without financial calculator

A loan is being repaid with 10 payments of 300 followed by 20 payments of 500 at the end of each year. The effective annual rate of interest is 5% for the first 10 years and 6% thereafter. 1) Calculate the amount of the loan. 2) Calculate the outstanding loan balance immediately after the 5-th payment has been made. 3) Calculate the outstanding loan balance immediately after the 15-th payment has been made