Two different computer systems are monitored for a total of n weeks. Let X_i denote the number of breakdowns of the first system during the ith week, and suppose the X_i’s are independent and drawn from a Poisson distribution with parameter μ₁. Similarly, let Yi denote the number of breakdowns of the second system during the ith week, and assume independence with each Y_i Poisson with parameter μ₂. Derive the mles of μ₁, μ₂, and μ₁ – μ₂.