According to a newspaper, customers are not settling for automobiles straight off the production lines. A sample of 188 recent purchases of a particular car model yielded a sample mean of $4,489 above the $20,200 base sticker price. Suppose the cost of accessories purchased for all cars of this model has a standard deviation of $1 ,412. a. Calculate a 90% condence interval for the average cost of accessories on this model. b. Determine the margin of error in estimating the average cost of accessories on this model. c. What sample size would be required to reduce the margin of error by 50%? a. The 90% condence interval for the average cost of accessories on the particular model is from $ to $ (Round to the nearest cent as needed. Use ascending order.) b. The margin of error in estimating the average cost of accessories on the particular model is $D. (Round to the nearest cent as needed.) c. A sample size of D is required to reduce the margin of error by 50%. (Round up to the nearest integer.)