the office manager of a small office ordered 120 packs of printer paper.based on average daily use, she knows that the paper will last about 40 days. what graph represents this situation? how many packs of printer paper should the manager expect to have after 10 days?

paper
[
150
[
100
[
50
___20___40___60 days

would it be 90 or 30 packs but then not sure which way graph goes upwards or downwards.
Can someone please try and maybe explain