2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/61064We consider directed graphs E which have been obtained by adding a sink to a fixed graph G. We associate an element of Ext(C*(G)) to each such E, and show that the classes of two such graphs are equal in Ext(C*(G)) if and only if the associated C*-algebra of one can be embedded as a full corner in the C*-algebra of the other in a particular way. If every loop in G has an exit, then we are able to use this result to generalize some of the classification theorems of Raeburn, Tomforde, and Williams for C*-algebras of graphs with sinks.24 pages, uses XY-pic, New version comments: small typos fixed, to appear in New York J. MathOperator Algebras46L55text