\begin{eqnarray}
    \Delta \mathbf{C}_{t+1} & = & (1-\Pi)\big(1+\underbrace{(\rfree/\Rfree)}_{\approx\,0}\big) \Delta \mathbf{C}_{t} + \underbrace{\Pi \xi_{t+1}}_{\equiv\,\epsilon_{t+1}} \label{eq:dCQuadSticky}
\end{eqnarray}
