The following table shows the marks obtained by two students in different subjects:
| Student A | Maximum marks | Student B | Maximum marks | |
|---|---|---|---|---|
| English | 60 | 100 | 80 | 150 |
| Psychology | 70 | 100 | 70 | 100 |
| History | 50 | 100 | 60 | 100 |
| Sanskrit | 30 | 50 | 15 | 25 |
The difference in the mean aggregate percentage marks of the students is