I got a invitation letter from the department of a university that I applied for to meet with the faculty and also to the open-house with paid air tickets and hotels. Is the invitation important or just a random choice of applicants? Does anyone has experience on it? What should I dress and do I need to contact the professor of interest before I arrive? I am not the U.S. citizen but are currently studying for the M.S. program in US. I have no idea what to do about this.Thanks.