$ABC$ is an isosceles triangle inscribed in a circle of radius r. If $AB=AC$ and $h$ is the altitude from $A$ to $BC$, then the triangle $ABC$ has perimeter $P=2(\sqrt{2hr-h^2})+\sqrt{2hr})$ and area $A$=_______also $\lim\limits_{h\to 0}\large\frac{A}{p^3}=$_______

Question

$\begin{array}{1 1}(a)\;A=h\sqrt{2rh-h^2},\lim\limits_{h\to 0}\large\frac{A}{p^3}=\frac{1}{128r}\\(b)\;A=h\sqrt{2rh-h^3},\lim\limits_{h\to 0}\large\frac{A}{p^3}=\frac{1}{28r}\\(c)\;A=h\sqrt{2rh^2-h},\lim\limits_{h\to 0}\large\frac{A}{p^3}=\frac{2}{128r}\\(d)\;A=3h\sqrt{2rh-h^2},\lim\limits_{h\to 0}\large\frac{A}{p^3}=\frac{3}{128r}\end{array}$