I am having problems with the plots. The two curves should look very close but there is a problem somewhere in my code

Hello, when i run this code, the plots that i get are not correct. The curves should be very close to each other but i think there is a problem somewhere in the code. Please let me know if you are able to debug it. The steps are correct and the equations were verified but the plot is not correct. The results in line 164 appears to be wrong because the number should decrease exponentially but it shows almost a constant number. Please advise

[Walter Roberson]

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