Please show all work/explanations, will provide positive feedback!

Bill, a university professor at the Ontario Business School, has been invited to attend a free lunch along with several colleagues. However, Bill has already purchased a ticket for a CPA luncheon and workshop on the same day. With respect to Bill decision of whether or not to attend the free lunch, which of the following is incorrect? a) The cost of the CPA luncheon ticket is a sunk cost. b) The cost of the CPA luncheon ticket is a period cost. c) The cost of the CPA luncheon ticket is an opportunity cost. d) The cost of the CPA luncheon ticket is the cost of the "free lunch." e) The cost of the CPA luncheon ticket may be claimed back from university