To study the birth weight of infants whose mothers smoke, a physician records the weights of 100 newborns whose mothers smoke. a. Find a 98% confidence interval based on for the mean birth weight of children of smoking mothers if the sample mean was found to be 6.1 pounds. Assume the population standard deviation is 2.1 pounds. b. Physician thinks that the margin of error is too large. Estimate the sample size required to estimate the mean birth weight within 0.3 pounds with a 98% confidence interval.