Please help me with these and show the steps

3. Ali has OMR 20,000 saved so far. He expects to save an additional OMR 1,500 a year at the end of each of the next fifteen years. If interest rate is 8% compounded annually, how much will he have saved at the end of this fifteen year period? 4. You wish to endow a chair in finance at a business school. If the interest rate is 10% per year and your aim is to provide OMR 200,000 a year in perpetuity, how much must be set aside today? The first payment will be made 1 year from today. 5. You have just obtained a 20-year mortgage loan of OMR 200,000. The loan has a 12\% annual interest rate compounded semiannually, and requires equal semiannual ( 6 months) payments beginning 6 months from now and continuing for 20 years. a. What will your semiannual payments be? b. How much is the remaining principal after 1 year, 5 years, 10 years, and 15 years