GMAT Math

I am trying to practice math problems at a certain difficulty level. Clearly, the higher numbered math problems in the OG book are of a higher difficulty level than the lower numbered problems.

Can anyone please provide me with a break down of where the 300-500, 500-600 and 700-800 level problems are? i.e. from from what number to what number in the OG book.

I hope that made sense. Thanks a lot.