Compond Interest and Annuity doubt!?

1)Mr. Paul borrows 20000 on condition to repay it with C.I. at 5% p.a in annual installments of .2000 each. The number of years for the debt to be paid off is?

2)A person invests 500 at the end of each year with a bank which pays interest at 10% p.a C.I. annually.The amount standing to his credit one year after he has made his yearly investment for the 12th time is?

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Compound interest and annuity