Which of the following are true statements?

a. The difference between how much a consumer is willing and able to pay and how much a consumer has to pay for a unit of a good is called consumer surplus.

b. An increase in supply will lead to a lower price and an increase in consumer surplus; a decrease in supply will lead to a higher price and a decrease in consumer surplus.

c. Both the difference between how much a consumer is willing and able to pay and how much a consumer has to pay for a unit of a good is called consumer surplus and an increase in supply will lead to a lower price and an increase in consumer surplus; a decrease in supply will lead to a higher price and a decrease in consumer surplus are true.

d. None of these is true.