Which of the following are true statements?

a. Producer surplus is the difference between what a producer is paid for a good and the cost of producing that good.

b. An increase in demand will lead to a higher market price and an increase in producer surplus; a decrease in demand will lead to a lower market price and a decrease in producer surplus.

c. We can think of the demand curve as a marginal benefit curve and the supply curve as a marginal cost curve.

d. Total welfare gains from trade to the economy can be measured by the sum of consumer and producer surpluses.

e. All of these are true statements