Plz see the picture

Suppose you run a day care for an office building and there are seven children A, B, C, D, E, F, G. You need to assign a locker where each child's parent can put the child's food. The children come and leave so they are not all there at the same time. You have 1 hour time slots starting 7: 00 a.m. to 12: 00 noon. A star in the table means a child is present at that time. What is the minimum number of lockers necessary? Show how you would assign the lockers. The contention matrix [1] of the problem is given below