When Caliban's will was opened it was found to contain the following clause:
I leave ten of my books to each of A, B, and C, who are to choose in a certain order.
No person who has seen me in a green tie is to choose before A.
If B was not in Oxford in 1920, the first chooser never lent me an umbrella.
If B or C has second choice, C comes before the one who first fell in love.
Unfortunately A, B, and C could not remember any of the relevant facts; but the family solicitor pointed out that, assuming the problem to be properly constructed (i.e. assuming it to contain no statement superfluous to its solution) the relevant data and order could be inferred. What was the prescribed order of choosing; and who first fell in love?
If you tackle this, remember that every statement is necessary. Also remember that the requirement (that the puzzle represented by the three statements is properly constructed) is not part of the original puzzle -- it is a meta-statement about the base puzzle. [People regularly get confused about this point.] One further point you have to consider -- was the family solicitor correct in claiming (a) that the relevant data could be inferred and (b) that the order be inferred.