An investment that pays interest quarterly (every 3 months) offers to triple your money in 6 years. What is the quarterly interest rate?

You plan to retire in 25 years. An investment fund will pay an 7% annual return for the first 15 years and then a 5% annual return for the last 10 years. How much would you need to invest today so that your investment fund has a value of one million dollars when you retire?