: $$\begin{aligned} P(u)&=&\left\{   \begin{array}{l} 0,    \hskip 00mm             u\le -a     \\   c\,\sqrt{u_0}\,J_{-\frac{0}{0}}(\frac{0}{0}u_0^{0/0}),                     \hskip00mm -a\le u\le 0         \\   \sqrt{u_0}\,\left[