When the price of coal fell from $300 a ton to $125 a ton, BHP Billiton cut production, laid off 6,000 workers, and closed some mines for six months. 3 tries left How did BHP Billiton's marginal cost change? What was the minimum average variable cost of the mines that closed temporarily. BHP Billiton's marginal cost ________, and the minimum average variable cost of the mines that closed temporarily was ________. A. remained at $300 a ton; $125 a ton B. fell from $300 a ton to $125 a ton; between $125 a ton and $300 a ton C. fell from $300 a ton to $125 a ton; $300 a ton D. remained at $300 a ton; $300 a ton