Q. A student must select 10 electives from four different departments, with at least one course from every department. The 10 courses are allocated to the four departments A, B, C, D in a manner which maximizes "knowledge."The student measures knowledge on a 100-point scale also comes up with the subsequent chart:

Number of courses
Department 1 2 3 4 5 6 ≥7
A 30 60 70 80 100 100 100
B 30 60 90 100 100 100 100
C 40 50 70 100 100 100 100
D 10 20 30 50 60 70 80
Explain how should the student select the courses?