What is the rule for this linear function?

Hello people, i have a math question that i need with, me, i will give the correct one brainiest, and for the other correct people, a and 5 stars.

Type the correct answer in each box. use numerals instead of words. if necessary, use / for the fraction bar. consider the given table.

Ellen makes and sells bookmarks. she graphs the number of bookmarks sold compared to the total money earned. why is the rate of change for the function graphed to the left?