Probability Question - Urgent

 Yvette had partied very late and didn't study for her morning supply chain management exam, going straight to bed.  She hoped she could do reasonably well  by simply guessing.  The exam contained 25 multiple choice questions, each with four choices and a grade of 60 or greater was necessary to pass.

1. What’s the probability that Yvette will pass just by guessing?
2. What if Yvette did a little bit of studying late at night and was able to eliminate one clearly wrong answer for each question; would she have a reasonable chance of passing? (i.e., now 3 choices instead of 4)
3. What if she stayed up all night studying and could eliminate two obvious incorrect choices for each question? (i.e., now 2 instead of 4)