A book publisher employs two typists, X and
Y. Typist X makes typographical errors at the rate of k per page, and Y makes
them at a different rate of r per page.
a. Considering that both X and Y do half of the entire publisher's typing, write down an expression for the PMF of the random variable E, the number of errors on a randomly chosen page.
b. Write down the PMF of E if the typist with the error rate k types 70 percent of the pages.
According to merging principle, my PMF should be distributed over Poisson(k+r) but I'm confused with the "half of the entire publisher's typing" and "70% of pages". I'm unable to incorporate this information. Any help would be appreciated.