One test that people who wish to donate blood must undergo is a test of iron level. Individuals with insuficient iron levels are not permitted to donate blood. A preliminary inexpensive screening test is initially performed for iron level. If an individual fails this test, he or she is given a more expensive second test of iron level. Suppose that 30% of the people who fail the first test pass the second test and are allowed to donate blood. A doctor is searching for a blood donor among those whil failed the first test. She randomly selects individuals from those who failed the first test.
What is the probability that the doctor will find a suitable donor on the
1) Second selection?
2) fourth selection?
3) tenth selection?