How to do multiplying radical expressing

The answer is

. I've demonstrated the 'split and combine' method in the image attached.
This principal is based on the fact that you can multiply and divide radicals as you would with regular integers, but you remember that the answers remain as radicals unless the number you're dealing with is a square (e.g. 9, 16, 25).

I'm just guessing, but my answer would c. 0 to 300.