Question: How many years did Michael Dante DiMartino work for an American animation studio owned by Waterman Entertainment?

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Zuko: Prince Zuko (祖寇 , Zǔ Kòu ) is a fictional character in Nickelodeon's animated television series "".  Created by Michael Dante DiMartino and Bryan Konietzko, the character is voiced by Dante Basco and is portrayed by Dev Patel in M. Night Shyamalan's 2010 film "The Last Airbender".

Avatar: The Last Airbender (season 3): Season Three (Book Three: Fire) of "", an American animated television series on Nickelodeon, first aired its 21 episodes from September 21, 2007 to July 19, 2008.  The season was created by Michael Dante DiMartino and Bryan Konietzko, and starred Zach Tyler Eisen, Mae Whitman, Jack DeSena, Jessie Flower, Dante Basco, Dee Bradley Baker, Greg Baldwin, Grey DeLisle and Mark Hamill as the main character voices.

Avatar: The Last Airbender (season 1): Season one (Book One: Water) of "", an American animated television series produced by Nickelodeon Studios, aired 20 episodes from February 21, 2005 to December 2, 2005.  The series was created by Michael Dante DiMartino and Bryan Konietzko, and starred Zach Tyler Eisen, Mae Whitman, Jack DeSena, Dante Basco, Dee Bradley Baker, Mako Iwamatsu and Jason Isaacs as the main character voices.

Bryan Konietzko: Bryan Konietzko (born June 1, 1975) is an American animation director, writer, producer and musician.  He is best known, together with Michael Dante DiMartino, as the co-creator and executive producer of the animated series "" and "The Legend of Korra".

Nickelodeon Animation Studio: Nickelodeon Animation Studio, also known in Burbank as Nickelodeon Studios Burbank, is an American animation studio owned and operated by Viacom through its television network Nickelodeon.  The studio produces many of the network's most popular animated series, including "SpongeBob SquarePants", "The Fairly OddParents", "Teenage Mutant Ninja Turtles", "Harvey Beaks", "The Loud House", "Bunsen Is a Beast", and "Welcome to the Wayne".  It also produces programs for Nicktoons Network, Nick at Nite, TeenNick, and Nick Jr. as well.

Michael Dante DiMartino: Michael Dante DiMartino (born July 18, 1974) is an American animation director best known as the co-creator, executive producer, and story editor of the animated TV series "" and "The Legend of Korra", both on Nickelodeon.  He was born in Shelburne, Vermont.  He studied at the Rhode Island School of Design with Bryan Konietzko, with whom he created "Avatar."  Before "Avatar," Mike worked for twelve years at Film Roman, helping to direct "King of the Hill", "Family Guy", and "Mission Hill" in addition to his own animated short, "Atomic Love", which was screened at a number of high-profile film festivals.  The dedication to his father's memory can be seen in the last episode of "Avatar: The Last Airbender".  In a 2010 interview the president of Nickelodeon, Cyma Zarghami, confirmed that DiMartino and Konietzko were developing a new series for the network, called "The Legend of Korra".  The series premiered on April 14, 2012, running 12 episodes for the first book "Air" and 14 for the second book "Spirits", which premiered on September 13, 2013 to 2.60 million viewers in the U.S., then the third book "Change" and the fourth and final book "Balance" of 13 episodes each.

Avatar: The Last Airbender (season 2): Season Two (Book Two: Earth) of "", an American animated television series on Nickelodeon, first aired its 20 episodes from March 17, 2006 to December 1, 2006.  The season was created and produced by Michael Dante DiMartino and Bryan Konietzko, and starred Zach Tyler Eisen, Mae Whitman, Jack DeSena, Jessie Flower, Dante Basco, Dee Bradley Baker, Mako Iwamatsu and Grey DeLisle as the main character voices.

Pete Waterman Entertainment: Pete Waterman Entertainment (PWE) is the production company one-time pop and dance record label owned by pop mogul Pete Waterman.  The label, originally PWL (Pete Waterman Limited), is most famous for being the home of hit record producers Stock Aitken Waterman.

Film Roman: Film Roman is an American animation studio owned by Waterman Entertainment, the production company of producer Steve Waterman.  Founded by veteran animator and director Phil Roman in 1984, it is best known for producing source animation for series such as "The Simpsons" (1992–2016), "King of the Hill" and "Family Guy" for 20th Century Fox Animation, as well as "Garfield and Friends" and various "Garfield" animated television specials.

The Legend of Korra (season 4): Book Four: Balance is the fourth and final season of the animated television series "The Legend of Korra" by Michael Dante DiMartino and Bryan Konietzko.  It consists of thirteen episodes ("chapters"), all animated by Studio Mir.  The episodes are made available on the Nickelodeon website and other online outlets each Friday beginning on October 3, 2014.  Critical reception of "Book Four", as of the series in general, was positive.

Supporting paragraphs: Michael Dante DiMartino Film Roman
Answer: twelve years