i am having issues presenting this code as 4 graphs since i keep getting this error can anyone point out where im going wrong

import matplotlib.pyplot as plt

import numpy as np

Distance=np.array([0,50,100,150])

I=int(input("input your desired interval "))

D1=[(0-x)**2 for x in range(0, 150,I)]

D2=[(50-x)**2 for x in range(0, 150,I)]

D3=[(100-x)**2 for x in range(0, 150,I)]

D4=[(150-x)**2 for x in range(0, 150,I)]

c=1000

h=400 #h=20 and this is 20**2

q=c*h #1000*400

r1 = [element + h for element in D1]

a1 = [element**1.5 for element in r1]

intensity1 = np.array([q/element for element in a1])

r2 = [element + h for element in D2]

a2 = [element**1.5 for element in r2]

intensity2 = np.array([q/element for element in a2])

r3 = [element + h for element in D3]

a3 = [element**1.5 for element in r3]

intensity3 = np.array([q/element for element in a3])

r4 = [element + h for element in D4]

a4 = [element**1.5 for element in r4]

intensity4 = np.array([q/element for element in a4])

print("the illumination intensity at every inteval for the 1st lamp: ",intensity1)

print("the illumination intensity at every inteval for the 2nd lamp: ",intensity2)

print("the illumination intensity at every inteval for the 3rd lamp: ",intensity3)

print("the illumination intensity at every inteval for the 4th lamp: ",intensity4)

plt.plot(intensity1, Distance)

plt.xlabel(’ intensity1(cd)’)

plt.ylabel(’ Distance(m)’)

plt.plot(intensity2, Distance)

plt.xlabel(’ intensity2(cd)’)

plt.ylabel(’ Distance(m)’)

plt.plot(intensity3, Distance)

plt.xlabel(’ intensity3(cd)’)

plt.ylabel(’ Distance(m)’)

plt.plot(intensity4, Distance)

plt.xlabel(’ intensity4(cd)’)

plt.ylabel(’ Distance(m)’)