In rectangle ABCD, AB=6 and AD=8. Point M is the midpoint of AD. What is the area of △AMC?<spanclass=′latex−bold′>(A)</span>12<spanclass=′latex−bold′>(B)</span>15<spanclass=′latex−bold′>(C)</span>18<spanclass=′latex−bold′>(D)</span>20<spanclass=′latex−bold′>(E)</span>24 2016 AMC 8AMC 8geometryrectangle