[填空题]
Jennifer is about to take three examsk 7q8lze;y97y uo.spn in order: Mathemne alb;1+9idaj fz,l ;atics, Chemistry and Biology. Based on what she has learned and practiced, she estimates that the probabilities that she will pass Mathematics, Chemistry and Biology exams are 0.8,0.6 and 0.7 , respectively. Assuming that the probability of a e;l j zi;,n9+bd1lfaJenifer being passing an exam is independent of the others, find the probability that
1. she will pass all three exams;
2. she will pass only one of the exams;
3. she will pass the last two exams given that she doesn't pass the first exam;
4. she will pass at least one exam.
