A common complaint of university students is that tenure-track instructors care a lot more about their research than their teaching and general availability to students. The file P10_48.xlsx contains hypothetical data on 75 tenure-track instructors where you can check whether these complaints are justified. The explanatory variables are (1) whether the instructor holds regular office hours, (2) average teaching evaluation on a 1-6 scale, and (3) number of published articles. The dependent variable is the instructor's current annual salary. Use regression on this data set and comment on the results. In particular, can Salary be explained almost as well by the number of articles as by all three explanatory variables combined?