Please help international trade law. Article XXIV OF GATT

Question 1 (20 points) Freedonia, Marketopia, and New Tucsonistan are three countries that wish to enter into a customs union. They want the new customs union to be compliant with GATT Article XXIV and therefore need to come up with a common external tariff for their products. They think it is a lot of work to do so with every single product listed in the tariff schedule, so have instead asked many different people to share the work load. They have asked you to determine the common external tariff for fountain pens and have provided you with the following data: Country Current Tariff Rate Percent of total imports Freedonia 5% 25% Marketopia 15% 45% New Tucsonistan 25% 30% What would be the common external tariff on fountain pens be