The Figure Below Shows the Demand (D) and Supply (S)

The figure below shows the demand (D) and supply (S) curves for Good X before and after a tax is imposed on each unit of the good sold.

-Refer to the figure above.If a per-unit tax of $3 is imposed on the sale of Good X,what is the tax revenue received by the government?

A) $20 million
B) $10 million
C) $12 million
D) $60 million