UPDATE:
If for instance $b>1.08148a^2$ then I replace $w$ by $w'$ such that $b(v,s,w') = 1.08148a^2$ and then I extract $\epsilon>0$ to guarantee that the new value $b'(v,s,w')<1.0848a^2$ as required. On the other hand I also need to guarantee that $q(a,b)<c<0$. Since I adjusted $b$, $q(a,b)$...