Suppose among 6 people there is a group of 3 people who either all know each or all 3 people are strangers to each other. (hint: this problem begs for a mathematical structure: draw six nodes or vertices in a circular pattern. then draw lines (with colors or one dotted the other solid) that denote whether the two vertices "know" or "not know" each other. see if you can show that no 3 people form a group as described above.