23. Two different computer systems are monitored for a total of n weeks. Let Xi denote the number of breakdowns of the first system during the ith week, and suppose the Xis are independent and drawn from a Poisson distribution with parameter 1. Similarly, let Yi denote the number of breakdowns of the second system during the ith week, and assume independence with each Yi Poisson with parameter 2.

Derive the mle’s of 1, 2, and 1  2. [Hint: Using independence, write the joint pmf (likelihood) of the Xis and Yis together.]