Part II - Birthweight Smoking.xlsx Data. The Birthweight Smoking.xlex dataset is from the 1989 linked National Natality- Mortality Detail files, which contains a census of infant births and deaths. The data are for births in Pennsylvania in 1989. These data were provided by Professors Douglas Almond, Kenneth Chay, and David Lee and are a subset of the data used in their paper "The Costs of Low Birth Weight," Quarterly Journal of Economics, August 2005, 120(3): 1031-1083. Use the data to complete the following: Problem 1. In the sample, a) What is the average value of Birthweight for all mothers