In Johnstown, the population is 80 and every single person drives by themselves to work. Each car on a road pollutes 10 pounds of carbon a year. A single bus pollutes 100 pounds of carbon a year. A bus can hold 40 people. The town decides to start running a bus and 25% of the people who used to drive now take the bus. How many fewer pounds of carbon are now emitted per year?
Please reason step by step, and put your final answer within \boxed{}.
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