Question: Zhang Heng (Chinese: Zhang Heng ; AD 78-139), formerly romanized as Chang Heng, was a Han Chinese polymath from Nanyang who lived during the Han dynasty. Educated in the capital cities of Luoyang and Chang'an, he achieved success as an astronomer, mathematician, scientist, engineer, inventor, geographer, cartographer, artist, poet, statesman, and literary scholar. Zhang Heng began his career as a minor civil servant in Nanyang. Eventually, he became Chief Astronomer, Prefect of the Majors for Official Carriages, and then Palace Attendant at the imperial court.

Zhang Heng is often credited with inventing the first odometer, an achievement also attributed to Archimedes (c. 287-212 BC) and Heron of Alexandria (fl. AD 10-70). Similar devices were used by the Roman and Han-Chinese empires at about the same period. By the 3rd century, the Chinese had termed the device the ji li gu che, or "li-recording drum carriage" (the modern measurement of li = 500 m/1640 ft). Ancient Chinese texts describe the mechanical carriage's functions; after one li was traversed, a mechanically driven wooden figure struck a drum, and after ten li had been covered, another wooden figure struck a gong or a bell with its mechanically operated arm. However, there is evidence to suggest that the invention of the odometer was a gradual process in Han Dynasty China that centered on the "huang men"--court people (i.e. eunuchs, palace officials, attendants and familiars, actors, acrobats, etc.) who followed the musical procession of the royal "drum-chariot". There is speculation that at some time during the 1st century BC the beating of drums and gongs was mechanically driven by the rotation of the road wheels. This might have actually been the design of Luoxia Hong (c. 110 BC), yet by at least 125 the mechanical odometer carriage was already known, as it was depicted in a mural of the Xiao Tang Shan Tomb. The south-pointing chariot was another mechanical device credited to Zhang Heng. It was a non-magnetic compass vehicle in the form of a two-wheeled chariot. Differential gears driven by the chariot's wheels allowed a wooden figurine (in the shape of a Chinese state minister) to constantly point to the south, hence its name. The Song Shu (c. AD 500 ) records that Zhang Heng re-invented it from a model used in the Zhou Dynasty era, but the violent collapse of the Han Dynasty unfortunately did not allow it to be preserved. Whether Zhang Heng invented it or not, Ma Jun (200-265) succeeded in creating the chariot in the following century.

Using a quote from the above article, answer the following question: When was this invented?
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Answer: c. 287-212 BC

Question: The Vienna Boys' Choir (German: Wiener Sangerknaben) or Vienna Choir Boys is a choir of boy sopranos and altos based in Vienna, Austria. It is one of the best known boys' choirs in the world. The boys are selected mainly from Austria, but also from many other countries. The choir is a private, not-for-profit organization.

Gerald Wirth became the choir's artistic director in 2001. However, since then, the choir has come under pressure to modernize and has faced criticism of their musical standards, leading to a split with the Vienna State Opera. The choir has for the first time had to advertise for recruits after a rival choir school was established by Ioan Holender, director of the opera company. He complained of both falling standards and poor communication with the choir. He said that the State Opera sometimes trained boys for particular stage roles, only to find out on the day of performance that they were unavailable as they had gone on tour with the choir. Some boys were attracted to the rival choir school by the prospect of a more relaxed atmosphere and of performance fees being paid directly to them. The Vienna Boys' Choir has sought to update its image, recording pop music selections and adopting an alternative uniform to the sailor suits used since the 1920s, allowing the boys to dance as they sing. After Eugen Jesser died in May 2008, Walter Nettig became the choir's president. Gerald Wirth has been the artistic director since 2001, and he also became the choir's president in 2013. In 2010, following sexual abuse allegations from two former choristers stemming from the late 1960s and early 1980s, the Vienna Boys' Choir opened a confidential phone and e-mail hotline to allow others to come forward. Eight possible victims came forward saying they were abused, either by staff or other choir members.

Using a quote from the above article, answer the following question: How large is the Vienna Boys Choir?
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Answer:
The choir has for the first time had to advertise for recruits