ABCD is a square with side of unit length. Points E and F are taken respectively on sides AB and AD so that AE \equal{} AF and the quadrilateral CDFE has maximum area. In square units this maximum area is:
<spanclass=′latex−bold′>(A)</span>21<spanclass=′latex−bold′>(B)</span>169<spanclass=′latex−bold′>(C)</span>3219<spanclass=′latex−bold′>(D)</span>85<spanclass=′latex−bold′>(E)</span>32