Keep in mind the question asked for highest and lowest respectively. If construed differently than the highest possible and then the lowest possible datatypes; we would still have to look at the largest difference in precedence that could be surmised by the precedence order.

http://msdn.microsoft.com/en-us/library/ms190309(SQL.90).aspx

Reading this question and then looking at the answers, we can see that each answer had two datatypes listed - thus respectively in those answers the first would be highest and the second would be lowest.

Pretty straight forward question and answer.