You are taking a very difficult chemistry course, which you must pass to maintain your scholarship and to avoid damaging your application for graduate school. Chemistry is not your strong suit, and, because of a just-below-failing average in the course, you will have to receive a grade of 90 or better on the final exam, which is two days away. A janitor, who is aware of your plight, informs you that he found the master for the chemistry final in a trash barrel and has saved it. He will make it available to you for a price, which is high but which you could afford. What would you do

Answer: Because the janitor is aware of your plight, the first thing to consider is this being a trick to extort you or to waste your time. After considering it to be a trick, you still have to consider it to be true. This makes it a game of 50:50 chance (that is equal chance to loss or win).

To approach this situation, you have to define an agreement with the janitor. The agreement should be "send me the chemistry master and I will pay you after I have written the exam to confirm it is actually a chemistry master or pay you 1/10 of your amount if it is not, to compensate your efforts". After sending this agreement, you should focused on your studies like you're not expecting a positive response from him.

Negotiation should not be involved in the agreement, as it will waste your time of studies.