$. In the second case, we set $r(b') := r_0$. Note that, in either case, $r(b')$ is a special arc and ${\varphi}( r(b')  ) \overset 0  = a_0^{b(0)+{\varepsilon}}$. In either case, we consider a bracket $b'$ such that $$b'(0) = b(0) , \ b'(0) = b(0)+0 , \ 