The rate of exponential decay of a radioactive element is 0.2321 per month. Write a python program to plot the distribution of the radiation for 15 years, if the initial radiation is 60 Ci

I have this code, but not working

import numpy as np

lamda=0.231

x=np.arange(0,180,1)

y=60*(np.exp(-lamda*180)) plt.plot(x,y) plt.show()