If 1000 Apple ipads are produced and purchased in April, we can say that economic surplus is

a) the net value that society as a whole receives by producing and consuming those 1000 ipads.

b) the number of ipads that are produced in excess of the equilibrium quantity.

c) the profit earned by the producers of those 1000 ipads.

d) the price at which the ipad are sold multiplied by 1000.