  For a row-finite graph G with no sinks and in which every loop has an exit,
we construct an isomorphism between Ext(C*(G)) and coker(A-I), where A is the
vertex matrix of G. If c is the class in Ext(C*(G)) associated to a graph
obtained by attaching a sink to G, then this isomorphism maps c to the class of
a vector which describes how the sink was added. We conclude with an
application in which we use this isomorphism to produce an example of a
row-finite transitive graph with no sinks whose associated C*-algebra is not
semiprojective.
