A class is comprised of 10 juniors 30 seniors and 10 graduat
     A class is comprised of 10 juniors, 30 seniors, and 10 graduate students. The final grades show that 3 of the juniors, 10 of the seniors, and 5 of the graduate students got an A. If a student is chosen at random and found to have carned an A, what is the probability that he/she is a senior?  The number of misspelled words found in student term project paper can be characterized by a Poisson distribution with lambda = 4.0/paper. Calculate the probability that there being more than two defects in a paper. 
  
  Solution

