6. Suppose an investment is made at an interest rate of 5% p.a. compounded twice a year. (a) If you invest an amount P now, give a formula for the balance after n six-month periods. (b) If you wish to have $10,000 in 8 years' time then how much must you invest? (c) If you invest $6000 now, how long would it take until you had $10,000