  The celebrated Mirror Theorem states that the genus zero part of the A model
(quantum cohomology, rational curves counting) of the Fermat quintic threefold
is equivalent to the B model (complex deformation, variation of Hodge
structure) of its mirror dual orbifold.
  In this article, we establish a mirror-dual statement. Namely, the B model of
the Fermat quintic threefold is shown to be equivalent to the A model of its
mirror, and hence establishes the mirror symmetry as a true duality.
