5. The manager of a commuter rail transportation system was recently asked by her governing board to determine which factors have a significant impact on the demand for rides in the large city served by the transportation network. The system manager collected data on variables thought to be possibly related to the number of weekly riders on the city's rail system. The file P10_20.xlsx contain these data. a. What do you expect the signs of the coefficients of the explanatory variables in this multiple regression equation to be? Why? (Answer this before running the regression.) b. Estimate a multiple regression equation using the given data. Interpret each of the estimated regression coefficients. Are the signs of the estimated coefficients consistent with your expectations in part a? c. What proportion of the total variation in the number of weekly riders is not explained by this estimated multiple regression equation