a. How long it takes for a sum of money to increase 25% at compounded interest of 5% per year? b. An air-condition is depreciated in such a way that the value of the air-condition at the end of any years is 85% of the value at the beginning of the year. The actual cost of that air-condition was Tk. 1,00,000/-, but it was sold only for Tk. 3,000/- due to some defects. Calculate the number of years the air-condition was in use