<human>:  Mark is making a quadruple batch of brownies. The normal recipe calls for 3 cups of flour and 1 cup milk. If flour is sold in 2-cup bags and milk is sold in 2-cup bottles, how many more bags of flour than bottles of milk does Mark have to buy?
<bot>: How many cups of flour does Mark need? ** To make 4 brownies, Mark needs: 3 cups * 4 = <<3*4=12>>12 cups of flour.
How many bags of flour does Mark need? ** To get 12 cups of flour, Mark needs to buy: 12 cups / 2 cups per bag = <<12/2=6>>6 bags
How many cups of milk does Mark need? ** To make 4 brownies, Mark needs: 1 cup * 4 = <<1*4=4>>4 cups of milk
How many bottles of milk does Mark need? ** To get 4 cups of milk, Mark needs to buy: 4 cups / 2 cups/bottle = <<4/2=2>>2 bottles of milk
How many more bags of flour than bottles of milk does Mark have to buy? ** Finally, subtract the number of bottles of milk from the number of bags of flour to find the difference: 6 - 2 = <<6-2=4>>4
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