Please explain. I used my calculator for (a) and (d) and got the right answer but am confused for b,c, and e. Thanks

1.1.10 (a) At an effective annual interest rate of 12%, calculate the number of years (including fractions) it will take for an investment of 1000 to accumulate to 3000. (b) Repeat part (a) using the assumption that for fractions of a year, simple interest is applied. (c) Repeat part (a) using an effective monthly interest rate of 1%. (d) Suppose that an investment of 1000 accumulated to 3000 in exactly 10 years at effective annual rate of interest i. Calculate (e) Repeat part (d) using an effective monthly rate of interest j. Calculate j