This is from "Financial maths" subject

Ordinary Simple Annuities & Ordinary General Annuities 3. An option of purchasing a car requires payments of $610 at the end of each month for the next three years. Suppose interest is 8.4% p.a. compounded monthly. How much is the interest cost? 20. Sarah deposits $300.00 into a savings account at the end of each month for five years. If the accumulated value of the deposits is $20000.00 and interest is compounded semi-annually, calculate the nominal rate of interest.