If you know the theory of Latin Square Design, you should do it by yourself. If you do not know the theory, I recommend you to go through your textbook to learn th theory. This is not the kind of question where people can help you.
a drug company wishes to test 4 different pain relievers A,B,C and D on 4 groups of subjects each day from Monday to Thursday. Use Latin square to design an experiment so as to reduce the effects due to difference between the subjects and different days.