Let O be the origin. Let OP=xi^+yj^−k^ and OQ=−i^+2j^+3xk^ , x,y∈R , x>0 , be such that ∣PQ∣=20 and the vector OP is perpendicular to OQ . If OR=3i^+zj^−7k^ , z∈R , is coplanar with OP and OQ , then the value of x2+y2+z2 is equal to
(1) 7
(2) 9
(3) 2
(4) 1