Replying to Stats problem. who is bored

Over time, a student analyzes her ability to guess correctly after narrowing down mutiple choice answers in a 5-selection question (choices a through e). She discovers that if she narrows her answer set to 2 or 3 choices, her probability the right answer is 0.8, but if she still has 4 or 5 choices 70% of the time, What is the probability that she will answer a question correctly any time she must guess? Draw the tree diagram & justify your answer.