Suppose you send an email to your instructor to request an appointment to discuss your test grade. Your instructor replies an email telling you to stop by her office at 12:30 pm the next day. At this point:

a. It is now common knowledge that you and your professor will meet tomorrow.
b. It is not common knowledge that you will meet tomorrow because your email exchange is private between your professor and you.
c. It may or may not be common knowledge depending on whether player are rational and self-interested.
d. It is not common knowledge that you will meet tomorrow.