Schrödinger's equation

Complete the code in Appendix C to take the parameter $E$ as input from the keyboard and solve the equation

$$\frac{d}{du}\left(\begin{array}{c}\Psi\\ \Psi'\end{array}\ri... ...si'\\ - 2 (E+1/r) \Psi \end{array}\right) \cdot \frac{dr}{du},$$

by integrating inwards from infinity with boundary conditions $\left(\Psi(u=1)=0, \Psi'(u=1)=1e-20\right)$ using N=200 intervals.