need help with this one

b) Alisya has been offered an investment that will pay her RM6,000 three years from today. If her opportunity cost is 8% compounded semiannually, what value should she place on this opportunity today and what is the most she should pay to purchase this payment today? (5 marks) c) You put RM10,000 in an account earning 5%. After a year, you make another deposit into the same account. Four years later (that is 7 years after your original RM10,000 deposit), the account balance is RM20,000. What was the amount of the deposit at the end of year 3? (6 marks) d) What is the difference between an ordinary annuity and annuity due? Which is more valuable? Why