I am a student pursuing an engineering degree and am taking an introductory course on nuclear engineering. One of our "computational exercises" is 
I don't understand the output I'm getting. I used y and x instead of N and t since I had read somewhere that N shouldn't be used. The output I'm looking for is e^-lambda(t) or in this case e^-lamda x. Can someone help me figure out where I'm going wrong?
Thanks
