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A supermarket chain wants to know whether consumers are willing to pay more for tea bags if there was a "Fair Trade" logo on the package. They introduce a variety of tea bags with the "Fair Trade" logo on it in a half of their stores, selected randomly. They collect data on sales of tea bags in all stores before and after the introduction of the new "Fair Trade" variety. They obtain the following regression estimates: Quantity = 100 + 40 I + 2 A + 10 A*I where quantity is the number of packs of tea bags sold, I=1 if the store was one where the new "Fair Trade" variety was introduced, and A=1 if the data is from after the introduction of new "Fair Trade" variety. What impact did the "Fair Trade" logo have on the quantity sold?

a,100 b,40 c,2 d,10