Let M be a
compact, orientable, irreducible, ∂-irreducible, anannular 3-manifold with
one component T of ∂M a torus. Suppose that r1 and
r2 are two slopes on T. In this paper, we shall show that if
M(r1) is
reducible while M(r2)
contains an essential annulus, then △(r1,r2)
≤ 2.