A computer generates paths along the vertices of the parellelogram above in such a way that its path consists of an edge, a diagonal, and an edge (always in that order), and the path never ends in the vertex it begins. For each vertex of a path, the computer generates a random number in such a way that the sum of the numbers along one diagonal is equal to the sum along the other. For a particular path, what is the number corresponding to vertex P

1) The sum of numbers of vertices Q and R is always 15 and vertex S carries number 4

2) the intersection of the diagonals, Q, carries number 2