A student must select 10 electives from four different departments, with at least one course from each department. The 10 courses are allocated to the four departments in a manner that maximizes "knowledge."The student measures knowledge on a lOO-point scale and comes up with the following chart:

No. of courses Department 1 2 3 4 5 6 ?;7 I 25 50 60 80 100 100 100 II 20 70 90 100 100 100 100 III 40 60 80 100 100 100 100 IV 10 20 30 40 50 60 70 How should the student select the courses?