Integrating
gives

Notice that
forces all terms in the sum to be 0, so that

and hence

making the first option correct.
Each pad of paper cost 3.25. Here is how I found it.
21.75 x 3 = 65.25
75 - 65.25 = 9.75
9.75 / 3 = 3.25
X = 3.25
Is this what you were looking for?
You can set up the relation as a table of ordered pairs.