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Find $P(X<3)$ and E(X).

I am a little confused with finding $P(X<3)$ and $E(X)$. Here, A,B,C are Poisson random variables with parameters 2.6,3, and 3.4, respectively. Let X be the number of errors typed in a manuscript. Each of three typists A,B,C are equally likely to type the manuscript with error rates given. For the $E(X)=\frac{1}{3}(2.6+3.4+3)=3$ but I am […]