The rial or riyal is the currency of Yemen. The estimated cost of Dubai Towers - Doha is 2.3 billion Qatari Riyal (US$620 million). The currencies of several Arabic countries are named rial or riyal after the Portuguese "real". It appeared on a 4 riyal Qatari stamp. In 1973, Amiri Decree No. 24 authorized the issuance of the Qatari Riyal (QR). The Saudi riyal ( ""); is the currency of Saudi Arabia. Enjoying infrastructure valued over 70 billion Saudi Riyal, ($ 18.7 billion). Consequently, the currency is sometimes referred to as the "Imadi riyal" or "Ahmadi rial". Nadec is a joint stock public company with 600 million Saudi Riyal equity capital. The Saudi Riyal lost half of its official value against the United States Dollar. The total value of the project was 44,600,000 Saudi Riyal. During his time as governor he revised the Saudi riyal. It replaced the Qatar and Dubai riyal at par. The riyal returned to its peg against the U.S. dollar in early December 2007. The Hejaz riyal was replaced by the Saudi riyal in 1925 at par.