You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.

[Q]: Category: I'M JUST RUNNING IN FOR... 
Clue: ...20 first-class stamps, which will now cost this much total
[A]: $7.40


[Q]: Category: MATHEMATICS 
Clue: Term for the side of a right triangle that is opposite the 90° angle
[A]: hypoteneuse


[Q]: Category: "THE" 
Clue: It's 2nd verse begins, "On the shore, dimly seen through the mists of the deep"
[A]:
"the star-spangled banner"