Using method of qualitative theory of ordinary differential equation, studies economic harvesting model with variable price and cost for a single population.

利用常微分方程定性理论的方法讨论了价格成本变化的单种群经济捕获模型。

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They can elect a consistent speed at a higher price or variable speeds for a discounted rate.

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"Two major energy companies are currently offering cheap fix deals at the same price as the cheapest variable deals, cutting many people's bills by hundreds of pounds and guaranteeing no price rises for up to two winters, " he said.

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The price of corn is a critical variable in the world food equation, and food markets are on edge because U.S. corn stocks are plummeting due to the ethanol mandate.

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