Thus the pullback e 1 of the epi e along t is also epi. Y 1 of x and f is 0 . T is an isomorphism as it is an epic strong mono. It follows that f and m are disjoint. Since f -1 is bounded and preserves meets, we only need to verify that it also preserves joins.
X are two strong subobjects.
X be the map induced by u and v. Y is a strong mono.