The Stop decay company sells an electric toothbrush for $25. Its sales have averaged 8,000 units per month over the past year. Recently, its closest competitor, Decay fighter, reduced the price of its electric toothbrush from $35 to $30. As a result, stop decay's sales declined by 1,500 units per month.
What is Stop decay's average monthly total revenue from the sale of electric toothbrushes before and after the price change determined?