Dear all,
There is a sign missing in the formulation of Assignment 4: In problem 3(b) the connecting homomorphism should be identified with plus-or-minus f_*. This does not affect the rest of the problem. (Also, a hint is that the inclusion from B to C(f) is not the correct map to write down in the short exact sequence in problem 3(b), one needs to insert signs depending on the degree to get a chain map from B to C(f)).
Alexander