(1) Sohail makes an initial investment of $20,000. In return, he receives $4,000at the end of one year and another $18,000 at the end of three years (a) Assuming that the investment is made at simple interest at rate r, write (b) Assuming that the investment is made at compound interest at effective down an equation of value for the investment and find r interest rate i, write down an equation of value for the investment and justify the statement that there is a unique yield rate. Use the "guess and check method" to estimate i to the nearest hundredth of a percent. (c) Starting with the same initial guess for i that you used in (b), check you answer using Newton's method. (d) (recommended for those with a BA ll Plus calculator) Use the Cash Flow worksheet to find i to the nearest millionth