Question: What occupation did both William Sellers and Joseph Whitworth have?

Context paragraphs:
Coleman Sellers II: Coleman Sellers II (January 28, 1827 – December 28, 1907) was a prominent American engineer, chief engineer of William Sellers & Co. professor of mechanics at the Franklin Institute, professor of engineering practice at Stevens Institute of Technology and inventor.  He obtained more than thirty letters-patent for inventions of his own, and served as presidents of the American Society of Mechanical Engineers in the year 1886-87.

William Sellers: William Sellers (September 19, 1824 – January 24, 1905) was a mechanical engineer, manufacturer, businessperson, and inventor who filed more than 90 patents, most notably the design for the United States standard screw thread.  As president of the Franklin Institute in Philadelphia, Pennsylvania, Sellers proposed the adoption of a system of screw threads which was easier for ordinary mechanics and machinists to cut than a similar design by Joseph Whitworth.  For many years, he led the machine tool firm of William Sellers & Co., which was a very influential machine tool builder during the latter half of the 19th century.

Sackville Street Building: The Sackville Street Building is a building on Sackville Street, Manchester, England.  The University of Manchester occupies the building which, before the merger with UMIST in 2004, was UMIST's "Main Building".  Construction of the building for the Manchester School of Technology began in 1895 on a site formerly occupied by Sir Joseph Whitworth's engineering works; it was opened in 1902 by the then Prime Minister, Arthur Balfour.  The School of Technology became the Manchester Municipal College of Technology in 1918.

70-pounder Whitworth naval gun: The 70-pounder Whitworth naval gun was designed by Joseph Whitworth during the 1860s.  It was a rifled muzzle loader and used his hexagonal, rifled-bore design.

Joseph Whitworth: Sir Joseph Whitworth, 1st Baronet (21 December 1803 – 22 January 1887) was an English engineer, entrepreneur, inventor and philanthropist.  In 1841, he devised the British Standard Whitworth system, which created an accepted standard for screw threads.  Whitworth also created the Whitworth rifle, often called the "sharpshooter" because of its accuracy and considered one of the earliest examples of a sniper rifle.

Whitworth Street: Whitworth Street is a street in Manchester, England.  It runs between London Road (A6) and Oxford Street (A34).  West of Oxford Street it becomes Whitworth Street West which then goes as far as Deansgate (A56).  It was opened in 1899 and is lined with many large and grand warehouses.  It is named after the engineer Joseph Whitworth whose works once stood along the route.  Whitworth Street West runs alongside the viaduct connecting Oxford Road and Deansgate railway stations: beyond Albion Street the Rochdale Canal is on the northern side.  On the Albion Street corner is the building once occupied by the Haçienda nightclub at nos. 11-13 while further east on the same side is the Ritz.

Soldiers of the Cross Church: The Evangelical International Church of the Soldiers of the Cross of Christ (also known as the Soldiers of the Cross Church but unrelated to Arnold Murray and Roy Gillaspie's organizations) was organized in the early 1920s by an American businessman named Ernest William Sellers, who began holding evening religious services at his place of business in Havana, Cuba.  After receiving a visit from a missionary named George Smith, Sellers was persuaded to organize a more active effort to evangelize Cuba with what he considered to be the proper understanding of the Bible.  Sellers enthusiastically recruited and sent missionaries throughout the island of Cuba, and served as the church’s spiritual leader during the remainder of his life.

120-pounder Whitworth naval gun: The 120-pounder Whitworth naval gun was designed by Joseph Whitworth during the 1860s.  It was a rifled muzzle loader and used his hexagonal rifled bore design, the principle of which is described in the article on the 70-pounder Whitworth naval gun.

Whitworth Hall: The Whitworth Hall on Oxford Road and Burlington Street in Chorlton-on-Medlock, Manchester, England, is part of the University of Manchester.  It has been listed Grade II* since 18 December 1963.  The Hall lies at the south-east range of the Old Quadrangle of the University, with the Manchester Museum adjoined to the north, and the former Christie Library connected to the west.  It was constructed c. 1895–1902, and was designed by Paul Waterhouse.  The official opening ceremony took place 12 March 1902, when the Prince and Princess of Wales (later King George V and Queen Mary) were present.  Whitworth Hall is named after Mancunian industrialist, Sir Joseph Whitworth, who bequeathed much of his fortune to fund public developments in Manchester.

William Sellers (colonial officer): William Sellers was a British colonial health official who introduced experimental instructional methods and propaganda to Nigerian cinema.  Sellers was the first director of the Colonial Film Unit, a unit initially developed to explain World War II to the African audience and build war support in the colonies but later became a medium for backing colonial development and the British way of life.  Sellers films had its share of critics, his filming technique was simple repetitive shots and plots with strict literal interpretations that a few other colonial era filmmakers like Julian Huxley felt was boring to the audience.

Supporting paragraphs: William Sellers Joseph Whitworth
Answer: engineer