Question: General Systems of Linear Equations

The matrix below shows which of 6 people in group A meets each of the 4 people in group B over a certain period. Some of the people in group A have highly contagious disease which is certain to be communicated if she/he meets a person from group B. it is found that at the end of the given period the first 3 in group B have contracted the disease. On the assumption that people do not mix with people from the same group and that no one in group B comes into contact with more than one infected person determine which members of group A had the disease.

(Rows should be labelled through to and columns should be labelled through to )