Model 4: Run a model with all the significant independent variables from model 1 as well as three new variables available in Case B, namely, Seerual, MgrSkill and CrewSkill. These new variables are in the worksheet labeled Data for Case B. Before running this model, see important notes 1 and 2 below. Question 15 model 4 the best model in terms of predicting profits (relative to other models you have run up to this point)? Also, please identify variables in Model 4 that do not contribute signicantly in predicting profit