I cannot understand where my professor got his answer from. Could you help?

The figure shows the market for shirts in the United States, where D is the U.S demand curve and S is the U.S. supply curve. The world price is $20 per shirt. The United States imposes a tariff on imported shirts, $4 per shirt.

In the figure above, U.S. consumers' ________ from the tariff is ________. loss; $176 million (he says this one)

gain; $64 million

loss; $80 million

gain; $128 million