Good question thanks Steve, but do I detect two possible answers, which is why the responses fall into two categories (at least so far)?
Yes, it's a good question. But the officially correct one of those two is in fact wrong, and the officially wrong one is in fact correct. It's a good question, but a terrible (wrong) answer and explanation.
I'll be surprised if anyone anwers anything other than one of those two answers, but I guess it could happen, some may (oh horror of horrors) select one of the other two.
Tom
Absolutely concur with everything you have said for the same reason, it came down to; are we being asked how to formulate a correct discount value or about data types, I figured whichever was answered it would be wrong!! In the end I just decided "I hope I am not being taught basic math!"