3. David plans to make monthly contributions to his retirement account until he retires in 25 years. One month after his last contribution, he will withdraw $3000/month for the next 10 years. Assume the retirement account earns interest at a rate of 6.8% compounded monthly. a. How much will be in David's retirement account when he retires if he plans to withdraw all of the money by the end of the first 10 years of retirement? b. How much should David deposit at the end of each month for the next 25 years to achieve his goal?