Directions: Study the following table carefully and answer the question.
Students studying various subjects in four different colleges.
| College | Arts | Science | Pharmacy | Library Science |
| A | 354 | 459 | 256 | 99 |
| B | 275 | 658 | 225 | 56 |
| C | 358 | 487 | 265 | 138 |
| D | 301 | 265 | 266 | 89 |
What is the difference between average strength per subject of colleges C and A?
1
20
2
25
3
24
4
21