you want to earn IDR 100,000,000 at the end of year 20. To achieve this goal, in the first 10 years you save IDR 1,000,000 at the end of each year and in the next 10 years you save IDR 1,000,000 + X. If the prevailing interest rate is J1 = 10.25%, then: a. calculate the value of X b. if you forget to save IDR 1,000,000 at the end of year 7 to the end of year 10, calculate the value of X