The Figure Shows the Market for Shirts in the United

Multiple Choice

The figure shows the market for shirts in the United States, where D is the domestic demand curve and S is the domestic supply curve. The world price is $20 per shirt. The United States imposes a tariff on imported shirts of $4 per shirt.
-In the figure above, the tariff ________ the domestic production of shirts in the United States by ________ per year.

A) increases; 8 million
B) decreases; 16 million
C) increases; 4 million
D) decreases; 8 million