Referring to the contingency table in Problem 4.8, if a large online retailer is selected at random, what is the probability that
a. you needed three or more clicks to be removed from an email list?
b. you needed three or more clicks to be removed from an email list in 2009?
c. you needed three or more clicks to be removed from an email list or were a large online retailer surveyed in 2009?
d. Explain the difference in the results in (b) and (c).