to be found from the boundary condition s of the wave function at x=0 and x=a. The wave function and its derivative have to be continuous everywhere, so. \psi_L(0)=\psi_C(0), \frac{d}{dx}\psi_L(0) = \frac{d}{dx}\psi_C(0), \psi_C(a)=\psi_R(a), \frac{d}{dx}\psi_C(a) = \frac{d}{dx}\psi_R(a). Inserting the wave functions, the boundary conditions give the following restrictions on the coefficients A_r+A_l=B_r+B_l