3 At the end of a revision course in mathematics, students have to pass a test to gain a certificate. The probability of any student passing the test at the first attempt is 0.85 . Those students who fail are allowed to retake the test once, and the probability of any student passing the retake test is 0.65 .

1. Draw a fully labelled tree diagram to show all the outcomes.
2. Given that a student gains the certificate, find the probability that this student fails the test on the first attempt.