A farmer has exactly 1,000 square feet of farmland, on which he can gr

We'd need to know about expenses to answer a "profit" question, so this should be asking about revenue. It's also a bit of a mystery why anyone would want to make that specific amount of profit. Anyway, for corn this farmer is making $30 per square foot (3 pounds per square foot at $10/pound). So if this farmer devoted half of his land to corn, and did nothing at all with the other half, he'd make $15 per square foot, and $15,000 in profit. That's way too high, so he must be devoting less than half his land to corn, and more than half to soy, and only D or E could be right. But it's very quick to rule out D also: that would mean 400 square feet of corn, and $12,000 in corn revenue, plus more than 6(600) = $3600 in soy revenue (since the 600 square feet of soy make at least $6 per square foot) which is again way too high. So E must be the answer, and if we really wanted to confirm that, we could, but that doesn't seem like it would be all that pleasant considering how complicated the setup is.