I'd like to know the reason why A) and C) is not the right answer.

Q15. Suppose there are only two types of cars, high quality ones worth 10000 (75% of the market for used cars) and lemons worth 5 000. Potential buyers do not know which cars are high quality, but they do know the proportion of high quality cars in the market. Sellers are happy to accept a price at least 75% of the value of the car. Which of the following statements are true? (a) The maximum buyers will pay for a car is 7500 (b) If the price in this market is set to 5000, all the cars will sell (0) There is a unique equilibrium price at which all the cars will sell