Final answer:
The equilibrium price and quantity of coffee will likely decrease due to the combined effects of increased wages for coffee-bean pickers (decreasing supply) and a decrease in the price of tea (decreasing demand for coffee).
Step-by-step explanation:
When considering the impact of increased wages for coffee-bean pickers and a decrease in the price of tea, a substitute for coffee, we need to analyze how both supply and demand will be affected. An increase in the wages of coffee-bean pickers represents an increase in production costs, which would shift the supply curve of coffee to the left, indicating a decrease in supply. This would typically result in a higher equilibrium price and a lower equilibrium quantity for coffee. On the other hand, a decrease in the price of tea would make tea more attractive to consumers, shifting the demand curve for coffee to the left, as some consumers substitute tea for coffee. This shift in demand would lead to a lower equilibrium price and quantity for coffee. Thus, the combined effect is a likely decrease in both the equilibrium quantity and the equilibrium price of coffee, making option c the correct answer: price will decrease and quantity may increase, decrease, or remain unchanged.