Roscoe Davis, chairman of a college's business department, has decided to apply a new method in assigning professors to courses next semester. As a criterion for judging who should teach each course, Professor Davis reviews the past two years' teaching evaluations (which were filled out by students). Since each of the four professors taught each of the four courses at one time or another during the two-year period, Davis is able to record a course rating for each instructor. These ratings are shown in the table. Find the best assignment of professors to courses to maximize the overall teachingrating.