The following graph depicts a large country that imports goods. $P^{**}$ is the international price. $P^H$ and $P^F$ are home price and foreign price for the same commodity when home is open. The difference between these two prices is exactly the import tariff imposed by the home country. Compared with the closed economy, when engaged in free trade, home country's producer surplus changes by

$($Question $5$ continued$)$ Compared with the closed economy, when engaged in free trade, home country's total surplus changes by

A$.a+b$

B$.a+b+c$

C$.b+d+e+f$

D$.a+b+c+d+e+f$

E$.-$a

F$.$ None of the above