There is a family of six persons A. B. C, D. E and F. They are Lawyer, Doctor, Teacher, Salesman, Engineer and Accountant There are two married couples in the family. D, the Salesman is married to the Lady Teacher. The Doctor is married to the Lawyer. F, the Accountant is the son of B and brother of E. C, the Lawyer is the daughter-in-law of A. E is the unmarried Engineer. A is the grandmother of F. How is D related to F?