The economy may be great as other countries had to pay a lot of money due to having to borrow money and also guns, weapons and other supplies however it might be negative because a lot of money was sent by them to help Britain and France
The reason why general douglas macarthur risk landing marines in enemy held territory at incheon was : That territory served as an important point in enemy's supply line.
By landing our troops here, we managed to cut out the supply of enemy's army, which brought a huge outcome that end the war.
Your answer is C hope this helps.