Sam bought a new fertilizer spreader for his yard. it has a dial on the handle that adjusts the flow of fertilizer. the dial setting is from 0 to 10. he has learned that if he sets the dial to 10, then one bag of fertilizer will cover only 600 square feet of his yard. the setting varies inversely with the area it will cover. how many square feet should one bag cover if the dial is set at 6?