When a firm's long-run average cost curve is horizontal for a range of output, then that range of production displays

Which of the following statements is true?

A) If both demand and supply increase there must be an increase in equilibrium price; equilibrium quantity may either increase or decrease. B) An increase in demand causes a change in equilibrium price; the change in price does not cause a further change in demand or supply. C) If demand decreases and supply increases one cannot determine if equilibrium price will increase or decrease without knowing which change is greater. D) A decrease in supply causes equilibrium price to rise; the increase in price then results in a decrease in demand.

Which of the following statements is the MOST accurate?

A) If PPP holds true, then the law of one price holds true for every commodity as long as the reference baskets used to reckon different countries' price levels are the same. B) If the law of one price holds true for every commodity, PPP must hold automatically. C) If the law of one price holds true for every commodity, PPP must automatically hold as long as the reference baskets used to reckon different countries' price levels are the same. D) If the law of one price does not hold true for every commodity, PPP cannot be true as long as the reference baskets used to reckon different countries' price levels are the same. E) If PPP holds true, then the law of one price must hold true automatically.