This document discusses maximum likelihood estimation for two related problems. It asks to (a) find the MLE of λ given a random sample from an exponential distribution with density f(x)=λe-λx for x>1, and (b) given a sample of n=50 observations where Yi=10 if Xi>3 and Yi=0 otherwise, and the sum of the Yi's is 20, to find the MLE of λ.