An online company lets you download songs for $0.99 each after you have paid a $5 membership fee. Which domain would be most appropriate to calculate the cost to download songs? *

A. rational numbers greater than zero

B. whole numbers greater than or equal to one

C. integers less than or equal to zero

D. whole numbers less than or equal to one

I assume that songs are $0.99 each. Let x represent the number of songs you download. Then the total cost of downloading x songs would be

C (x) = $5.00 + ($0.99/song) x

and ONLY integers = to or greater than 0 make sense here. The domain is [0, 100) assuming you cannot buy more than 100 songs.

Personally I'd give the answer as "2, whole numbers more than or equal to zero." However, IF you don't pay the membership fee until ready to actually order one or more songs, then "2, whole numbers greater than or equal to one" makes sense. You'd pay $5 plus $0.99 for one song, in that case.