Answer:
a. a decrease in the price of wool shirts and a decrease in the price of raw cotton
Explanation:
A decrease in the price of wool shirts would lead to an increase in demand for wool shirts and a decrease in demand for cotton shirt. Cotton and wool shirts are substitutes goods. Price would fall and quantity would fall. A decrease in the price of raw cotton would increase production of cotton shirts and the supply of shirts would increase. This would lead to a rightward shift in the supply curve. Quantity would increase and price would fall. The combined effect of this would lead to an unambiguous decrease in price.
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