The table below shows the results of a survey asking students about their favorite subject and their grade level.
| Subject | 9th | 10th | 11th | 12th | Total |
|---|---|---|---|---|---|
| Math | 15 | 10 | 8 | 7 | 40 |
| Science | 12 | 14 | 10 | 4 | 40 |
| English | 8 | 11 | 12 | 9 | 40 |
| History | 5 | 5 | 10 | 10 | 30 |
| Total | 40 | 40 | 40 | 30 | 150 |
Given that a randomly selected student's favorite subject is Math, what is the probability that the student is in 9th grade?
