Answer the question from the given passage. Your answer should be directly extracted from the passage, and it should be a single entity, name, or number, not a sentence.

Passage: On October 6, 1973, Syria and Egypt, with support from other Arab nations, launched a surprise attack on Israel, on Yom Kippur. This renewal of hostilities in the Arab–Israeli conflict released the underlying economic pressure on oil prices. At the time, Iran was the world's second-largest oil exporter and a close US ally. Weeks later, the Shah of Iran said in an interview: 'Of course [the price of oil] is going to rise... Certainly! And how!... You've [Western nations] increased the price of the wheat you sell us by 300 percent, and the same for sugar and cement... You buy our crude oil and sell it back to us, refined as petrochemicals, at a hundred times the price you've paid us... It's only fair that, from now on, you should pay more for oil. Let's say ten times more.' Question: Who was the world's second largest oil producer?
Iran

Passage: Between Bingen and Bonn, the Middle Rhine flows through the Rhine Gorge, a formation which was created by erosion. The rate of erosion equaled the uplift in the region, such that the river was left at about its original level while the surrounding lands raised. The gorge is quite deep and is the stretch of the river which is known for its many castles and vineyards. It is a UNESCO World Heritage Site (2002) and known as 'the Romantic Rhine', with more than 40 castles and fortresses from the Middle Ages and many quaint and lovely country villages. Question: What flows between Bingen and Bonn?
Middle Rhine

Passage: Warsaw's first stock exchange was established in 1817 and continued trading until World War II. It was re-established in April 1991, following the end of the post-war communist control of the country and the reintroduction of a free-market economy. Today, the Warsaw Stock Exchange (WSE) is, according to many indicators, the largest market in the region, with 374 companies listed and total capitalization of 162 584 mln EUR as of 31 August 2009. From 1991 until 2000, the stock exchange was, ironically, located in the building previously used as the headquarters of the Polish United Workers' Party (PZPR). Question: Whose former headquarters was the WSE located in until 2000?
Polish United Workers' Party