Quantum cliff with python

i am trying to plot wavefunction which is scattered by a step function. I referred Griffith quantum mechanics 2nd edition problem 2.35. here, the energy is E=V/3 and i set V=3. the shape of the potential looks like cliff, left side of the cliff is higher than the right side one.

Then, i am trying to find reflection coefficient for this and i just compared the height of the wavefunction; left with respect to the step function is 2, and right is 1.7, and i got a reasonable value of reflection probability; 0.15 but the exact answer is 0.11111

My question is that is this code is correct or i just got a right answer by chance???

    import matplotlib.pyplot as plt
    %matplotlib inline
    from scipy.integrate import odeint
    import numpy as np

    def ps(y,t):
        if t<10:
            u=0
        else:
            u=-3
        psi=y[0]
        dpsi=y[1]
        dp=dpsi
        dp2=(-1+u)*psi
        return [dp,dp2]
    yo=[2,0]
    t=np.linspace(0,100,400)
    psis=odeint(ps,yo,t)    
    #plt.ylim(-3,3)
    plt.xlim(0,20)
    plt.plot(t,psis[:,0],'r')

    plt.plot([0,10,10,40],[0,0,-3,-3],'g')