Carlson bought land that cost $8000 and additional land that cost $4000. He initially owned 300 square meters of land. If the land he bought costs $20 per square meter, how big is his land after buying the new land? Let's be accurate as possible.

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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Carlson bought land that cost $20 per square meter, therefore the size of the land he bought is 8000 / 20 = 400. And the size of the other land he bought is 4000 / 20 = 200. Therefore the total size of the land he owns is 400 + 200 + 300 = 900.
The answer: 900.