Question: Who was the American screenwriter for 2008 American comedy film directed by Tom Vaughan and starring Cameron Diaz and Ashton Kutcher?

Context paragraphs:
Dude, Where's My Car?: Dude, Where's My Car?  is a 2000 American comedy film directed by Danny Leiner.  The film stars Ashton Kutcher and Seann William Scott as two young men who find themselves unable to remember where they parked their vehicle after a night of recklessness.  Supporting cast members include Kristy Swanson, Jennifer Garner, and Marla Sokoloff.

Guess Who (film): Guess Who is a 2005 American comedy film about race relations directed by Kevin Rodney Sullivan.  It is a loose remake of the 1967 film "Guess Who's Coming to Dinner", in the form of a romantic comedy.  While the 1967 film covered interracial romance of a black man with a white woman, the 2005 film covered the topic of a white man with a black woman.  The film stars Bernie Mac, Ashton Kutcher, and Zoe Saldana.

Bad Teacher: Bad Teacher is a 2011 American comedy film directed by Jake Kasdan based on a screenplay by Lee Eisenberg and Gene Stupnitsky, and starring Cameron Diaz, Justin Timberlake, Lucy Punch, Jason Segel, and Phyllis Smith.

Ashton Kutcher: Christopher Ashton Kutcher ( ; born February 7, 1978) is an American actor and investor.  Kutcher began his career as a model and began his acting career portraying Michael Kelso in the Fox sitcom "That '70s Show," which aired for eight seasons.  He made his film debut in the romantic comedy "Coming Soon" and became known by audiences in the comedy film "Dude, Where's My Car? ", which was a box office hit.  In 2003, Kutcher appeared in romantic comedies "Just Married" and "My Boss's Daughter" and, the same year, he created, produced, and hosted "Punk'd" which aired on MTV for five seasons until its revival in 2012.  In 2004, Kutcher starred in the lead role of the psychological film "The Butterfly Effect" and gained public recognition.

What Happens in Vegas: What Happens in Vegas is a 2008 American comedy film directed by Tom Vaughan, written by Dana Fox and starring Cameron Diaz and Ashton Kutcher.  The title is based on the Las Vegas marketing catchphrase "What happens in Vegas, stays in Vegas."

The Invisible Circus (film): The Invisible Circus is a 2001 American drama film written and directed by Adam Brooks and starring Cameron Diaz, Jordana Brewster, and Christopher Eccleston.  Based on the 1995 novel "The Invisible Circus" by Jennifer Egan, the film is about a teenage girl who travels to Europe in 1976 in search of answers to her older sister's suicide.  During her search, she falls in love with her dead sister's former boyfriend.  The film premiered at the Sundance Film Festival on January 11, 2001, and was released in the United States on February 2, 2001.

Knight and Day: Knight and Day is a 2010 American action comedy film starring Tom Cruise and Cameron Diaz.  The film, directed by James Mangold, is Cruise and Diaz's second on-screen collaboration following the 2001 film "Vanilla Sky".  Diaz plays June Havens, a classic car restorer who unwittingly gets caught up with the eccentric secret agent Roy Miller, played by Cruise, who is on the run from the CIA.

Dana Fox: Dana Fox (born July 16, 1976) is an American screenwriter best known as the writer of "The Wedding Date" (2005), "What Happens in Vegas" (2008) and the television comedy series "Ben and Kate".

Killers (2010 film): Killers is a 2010 American action comedy film directed by Robert Luketic and starring Katherine Heigl and Ashton Kutcher.  The film was released on June 4, 2010.  The film centers on a young woman (Heigl) who meets the man of her dreams (Kutcher) who turns out to be an assassin.

My Sister's Keeper (film): My Sisters's Keeper is a 2009 American drama film directed by Nick Cassavetes and starring Cameron Diaz, Abigail Breslin, Sofia Vassilieva, and Alec Baldwin.  Based on Jodi Picoult's novel of the same name, On June 26, 2009 the film was released to cinemas in the United States, Canada, Ireland, Mexico, and the United Kingdom.

Supporting paragraphs: Dana Fox What Happens in Vegas
Answer: Dana Fox