Exercise . Quarry Modeling. Background Note: The density of an object is its mass divided by its volume. Hence mass is density times volume, and volume is mass divided by density. Two types of rock are mined in a quarry. "Softrock" has an density of 5 Tonnes per cubic metre, and "hardrock" has a density of 8 Tonnes per cubic metre. Up to 600 Tonnes of softrock can be mined each hour, and independent of this, up to 300 Tonnes of hardrock can be mined each hour. The mined rock is crushed and then travels on a conveyor belt. (To avoid mixing the two types of rock they will crush one type of rock, then switch over to the other type, and then keep switching back and forth). The conveyor belt can handle up to 110 cubic metres of rock per hour. The crusher can handle up to 1000 Tonnes per hour when crushing softrock, or up to 400 Tonnes per hour when crushing hardrock. The company makes $10/ Tonne for softrock and $14/ Tonne for hardrock. The quarry operator wishes to know how many Tonnes of each type of rock they should produce each hour?