A loan of $39999.85 is to be repaid by payments at the end of each quarter for eight years. Each payment is 2% higher than its predecessor. The loan is made at the nominal rate of discount of 4% convertable quarterly.Find the balance just after the 20th payment, the amount of interest in the twentieth payment, and the amount of principal in the twentieth payment.

I am getting answers different than the book.

For interest I get $214.84 but the book says it should be $$217.23.

For the principal I get $1357.40 and it should be $1357.73.

And for the balance after the 20th payment, I get $20,126.16 and it should be $20,147.74.

I know they are not that far off but I want to see what I am doing wrong. here. Thank you!