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on 11 If corn and wheat are substitutes an increase in demand of corn will take place..... red . a. When the prices of corn increases d out of O b. None of these O c. When the prices of wheat increases on O d. When the prices of wheat decreases on 12 Which of the following factors cause a contraction in quantity demanded for a commodity? red O a. A decrease in the price of complementary goods d out of O b. A rise in the price of the commodity O c. An increase in the price of its substitutes on . d. An increase in the taste and preferences of the consumer for the commodity on 13 The Opportunity Cost concept in economics is useful for red a. To understand the importance of efficiency in the usage of resources d out of O b. To know the concept of sacrifice of output in usage of resources . c. All of these on O d. Allocating resources for various requirements in an economy