How many pairs of positive integers (x,y) are there such that xy−71x+30=0?<spanclass=′latex−bold′>(A)</span>8<spanclass=′latex−bold′>(B)</span>18<spanclass=′latex−bold′>(C)</span>72<spanclass=′latex−bold′>(D)</span>2130<spanclass=′latex−bold′>(E)</span>Infinitely many