5. Vella and Verbeek (1998) use the National Longitudinal Survey Youth Sample dataset to study the impact union membership has on wages for young males. You can get the dataset from here. (a) Create a variable equal to the exponential of lwage. (b) Generate a new variable that represents the annual salary (for each observation) (c) Collapse the data to obtain the mean annual salary by year and ethnic|racial group, black, hispanic, other, etc. (d) Generate a line graph showing the mean annual salary over time for each ethnic|racial group