Refer to Exercise 4.99, and further suppose that the 5 respondents who are below 30 consist of 2 males and 3 females, whereas those above 30 consist of 4 males and 2 females. Now, the researcher wants to randomly select 2 males and 2 females to be assigned to the treatment regimen. (The random selections from the different sexes are, of course, independent.)
(a) How many selections are possible?
(b) What is the probability that both selected males are over 30 and both selected females are under 30?