May I request assistance for a mathematical problem. The problem arises this way. I’m a litigation lawyer in private practice. In one of my cases the opposing lawyer claims that he “overlooked” a letter that I sent him. However he didn’t overlook any of the other 48 letters that I sent him. It just so happens that he “overlooked” the one letter that has serious consequences. My normal practice is to send letters by facsimile and then send the original by ordinary post. So the opposing lawyer “overlooked” this particular letter twice – once when it was sent by facsimile and again when he received it through the post. I’d like to know the mathematical chances of his story being true. There are altogether 49 letters sent twice – once by facsimile and once through the post – being 98 receptions altogether. Out of those 98 receptions he overlooks two letters. But they happen to be the facsimile and original of the same letter. The chances of that seem remote to me. I would like to know is there a formula that can calculate the chances of doing this? I haven't attempted this because I wouldn't know where to start.