Graph theory. solve this question properly.

Question 6: In a school, there are four teachers X1,82,83,84 and five batches Y1,Y2,Y3,74,Y5. Given that teacher Xi is required to teach batch Yj for Pij periods (for example, X1 has to take 2 classes with batch Y1, 1 class with batch Y4], schedule a complete routine in the minimum possible number of periods. The matrix is given below: X1 X2 X3 X4 Y1 2 2 Y2 1 2 Y3 2 Y41 2 1 Y5 1 1 Remember there are only 3 class rooms available. == OSIM