Suppose a large country A initially imposed a tariff on its imports and is now considering removing its tariff. Use a domestic-market graph to:

a) show the effect of country A's tariff removal on the world's price, country A's import price, import quantity, consumer surplus, producer surplus, and government revenue.

b) identify country A's net welfare change as a result of its tariff removal. Is country A unambiguously better off?

c) Use a different graph to show how foreign producers will be affected by country A's tariff removal?

d) What factor determines the level of optimal tariff for country A?