Exercise 12, § 2

Soit $(C, d', d'')$ un bicomplex, such that one has $H''_{p,-p}(C) = 0$ for all $p \in \mathbf{Z}$, $H'_{-q,q+1}(C) = 0$ for $q \geqslant 0$, $H'_{r,-r-1}(C) = 0$ for $r \geqslant 0$, and that there exist positive integers $a$ and $b$ such that $C_{a,-a} = C_{-b,b} = 0$. Exercise prove that the a-module $H'_0,0(C)$ is zero.