A computer generates paths along the vertices of the parallelogram above. It moves in such a way that its path always consists of a side, a diagonal, and then a side and it never ends at the same vertex it begins with, i.e., PQ → QOS → SR. For each vertex on a path, the computer generates a random number. The sum of the numbers on one diagonal is equal to the sum on the other. For a given path, what is the number generated for vertex P?
1. The sum of Q and R is always 15 and S carries number 4.
2. The intersection of the diagonals, O,carries number 2.