Question 5. (10 points) Using data on birth weights, we estimate the following models: bwght; = B1 + Bzcigs; + ui bwght is birth weight (in ounces), cigs is the number of cigarettes smoked daily during pregnancy a. (3 points) We want to estimate the impacts of smoking duing prenancy on baby's birth weights. Discuss the potential omitted variable bias and it consequences on the OLS estimator B2 b. (7 points) Adding family income variable (famine) to the model as follows: bwght; = a1 + azcigs; + asfaminc + ui Clearly explain if adding faminc to the model increases or decreases the impacts of cigs on bwght ? [Hint: Derive the relationship between B2 and a2 and compare the two value ]