It is decided to conduct a tennis tournament consisting entirely of double matches. Four tennis players (denoted by A,B,C,D) are going to playing the tournament. Each pair {W, X} of tennis players will play a match against every other pair {Y, Z} of tennis players, where then {W, X} N{Y, Z} = 0, but no 2-person team is to play two matches on the same day. What is the minimum number of days needed to schedule such a tournament? Give an example of such a tournament using a minimum number of days. (10 Marks)