That Ain't Hay!

Farmer Brown has hay and clover planted as shown. He has more square meters devoted to hay than clover.

Farmer Brown harvests his clover and hay and takes them to town to sell. He fetches $0.25 per kilogram for his clover and $0.10 per kilogram for his hay. At the end of the day, he has made more than $300, but less than $400 from selling his crops.

If the side lengths of the large square and small square are both integers (in meters), and Farmer Brown gets 1 kg of crop per square meter of field, what are the minimum dimensions of the large square?

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