Please help with the homework

4. An investment of R22 000 has been made on your behalf for the next 6 years, compound interest. How much will this investment be worth if: (a) the rate of interest is 10% p.a. (b) interest is paid at 7% p.a. for the first R 1000,9% p.a. for the next R5 000 and 12% p.a. for the remainder. (c) the rate of interest is 9% p.a. but paid on a six-monthly basis