Study the following table carefully and answer the following question.
Subject
(Full Marks 50) | 40 and above | 30 and above | 20 and above | 10 and above | 0 and above |
| Physics | 9 | 32 | 80 | 92 | 100 |
| Chemistry | 4 | 21 | 66 | 81 | 100 |
| Aggregate | 7 | 27 | 73 | 87 | 100 |
What is the difference between the number of students passed with 30 as cut – off marks in chemistry and those passed with 30 as cut – off marks in aggregate?