Legal and Logical

After having failed his exam in  "Logistics and Organization", a student goes and confronts his lecturer about  it. Student, "Sir, do you really understand anything about the  subject?" Professor, "Surely I must. Otherwise I would not be a  professor!" Student, "Great, well then I would like to ask you a  question. If you can give me the correct answer, I will accept my mark as is and  go. If you however do not know the answer, I want you give me an 'A' for the  exam." Professor, "Okay, it's a deal. So what is the  question?" Student: "What is legal, but not logical, logical, but not  legal, and neither logical, nor legal?" Even after some long and hard  consideration, the professor cannot give the student an answer, and therefore  changes his exam mark into an 'A', as agreed. Afterwards, the professor  calls on his best student and asks him the same question. He immediately  answers, "Sir, you are 53 years old and married to a 23 years old woman, which is  legal, but not logical. Your wife has a 25 year old lover, which is logical, but  not legal. The fact that you have given your wife's lover an 'A', although he  really should have failed, is neither legal, nor logical."