Algebra question in algebraic topology

[quasar987]

In Hatcher, p. 262 (http://www.math.cornell.edu/~hatcher/AT/ATch3.4.pdf), he writes, just before Lemma 3A.1, "the next lemma shows that this cokernel is just H_n(C)\otimes G. I can't say that I see how this follows.

Thanks!

 

[quasar987]

Ok I see it now. It just comes from tensoring the exact sequence B_n-->Z_n-->H_n-->0.