5.42 Number of colony-forming units. In microbiology, colony- forming units (CFUs) are used to measure the number of microorganisms present in a sample. To determine the number of CFUs, the sample is prepared, spread uniformly on an agar plate, and then incubated at some suitable temperature. Suppose that the number of CFUs that appear on the agar plate after incubation follows a Poisson distribution with p = 9. a. If the area of the agar plate is 75 square centimeters (cm2) , what is the probability of observing no CFUs in a 25 cm2 area of the plate? b. If you were to count the total number of CFUs in ve plates, what is the probability that you would observe more than 60 CFUs? Use the Poisson distribution to obtain this probability. c. Repeat the probability calculation in part (b) but now use the Normal approximation. How close is your answer to your answer in part (b)