Coppock curve is defined as the following:
$$z_{k+1} = Coppock = WMA[10] \; of \; (ROC[14] + ROC[11])$$
where $ROC[14]$ is percentage rate of change of the current value of input $s$ with respect to the one that is 14 steps behind, i.e.,
$$ ROC[14] = x_{k+1}=100\frac{s_k-s_{k-14}}{s_{k-14}} $$ Similarly, $$ ROC[11] = y_{k+1}=100\frac{s_k-s_{k-11}}{s_{k-11}} $$ and $WMA[10]$ is the weighted moving average for a window including 10 values, i.e.,
$$ z_{k+1}=\frac{1}{\sum_{i=1}^{10}i}\sum_{i=1}^{10} 1\times(x_{k-10}+y_{k-10})+2\times(x_{k-9}+y_{k-9})+\dots+10\times(x_{k+1}+y_{k+1}) $$
Note that the above is valid when we have access to 14 previous values of $s$. My questions:
1- Coppock curve is supposed to catch the lowest or highest of the curve, why its setup makes it possible to do that?
2- Instead of $14$, $11$, or $10$ we can go with any integers? What would be the effect of changing them?