**Concept:** The question tests on the basics of Counting

**Solution:**

Take the 5 Math books as 1 unit, 4 Physics books as 1 unit and 2 chemistry books as 1 unit.

Externally, we can arrange these 3 units in 3! ways.

internally, the math books can be arranged in 5! ways, Physics in 4! ways and chemistry books in 2! ways.

Total Arrangements = 3! * 5! * 4! * 2!

**Option a **