Math Quiz: NYT Learning Network

Through Math for America, I am part of an on-going collaboration with the New York Times Learning Network.  My latest contribution, a Test Yourself quiz-question, can be found here:

https://learning.blogs.nytimes.com/2012/04/16/test-yourself-math-april-16-2012/

This question is based on the current oil-export capacity of Iran.  How long would it take Iran to export a billion dollars’ worth of oil?