A parabola y=ax2+bx+c has vertex (4,2). If (2,0) is on the parabola, then abc equals<spanclass=′latex−bold′>(A)</span>−12<spanclass=′latex−bold′>(B)</span>−6<spanclass=′latex−bold′>(C)</span>0<spanclass=′latex−bold′>(D)</span>6<spanclass=′latex−bold′>(E)</span>12