Data Sufficiency

Hi all, recently took a practice exam and struggled with the following question. Although I know the right answer now, I'm still not sure how it works or how to get there. Any help on how to go about solving this would be appreciated!

Question:
The cost of a square slab is proportional to its thickness and also proportional to the square of its length. What is the cost of a square slab that is 3 meters long and 0.1 meter thick?

1. The cost of a square slab that is 2 meters long and 0.2 meter thick is $160 more than the cost of a square slab that is 2 meters long and 0.1 meter thick.

2. The cost of a square slab that is 3 meters long and 0.1 meter thick is $200 more than the cost of a square slab that is 2 meters long and 0.1 meter thick.

I can see that you can obviously arrive at the answer with both statements together, but that's not the correct answer