pls answer :) it would be a very big help for me. i will use it to check my work, thank you so much!

6. A refinery estimates that one of its furnaces will require maintenance Php 20,000,000.00 at the end of 2 years, Php 40,000,000.00 at the end of 4 years and Php 80,000,000.00 at the end of 8 years. What uniform semi-annual amounts could it set aside over the next eight years at the end of each period to meet these requirements of maintenance cost if all the funds would earn interest at the rate of 6% compounded semi-annually? 7. A pump can be bought for Php 10,000 php or for Php 2,000 down and the interest rate is 4.61% per year for 15 years. What is the annual payment? 8. A mining firm is offered for sale for Php 5.7M. On the basis of estimated production, an annual rate of return is expected to be 6.7% in which after 10 years, the firm will be worthless. What annual payment is needed