please help number 3 and 4

3. Simple interest of i = 4% is being credited to a fund. In which period is this equivalent to an effective rate of 2.5%? 4. An amount of money is invested for one year at a rate of interest of 3% per quarter. Let D(k) be the difference between the amount of interest earned on a compound interest basis and on a simple interest basis for quarter k, where k = 1,2,3,4. Find the ratio of D(4) to D(3)