Figure $9-4$

QUANTITY $($Earrels of crude oil$)$

Refer to Figure $9-4.$ When the country for which the figure is drawn allows international trade in crude oil,

a$.$ consumer surplus changes from the area $A$ to the area $A+B.$

b$.$ consumer surplus changes from the area $A+B+D$ to the area $A.$

c$.$ producer surplus changes from the area $C$ to the area $B+C+D.$

d$.$ total surplus decreases by the area D$.$