Question: According to Katy Perry, California Gurls is an answer song to what song by Jay-Z that featured vocals by Alicia Keys?

<P0-S0> American singer Katy Perry has released five studio albums, one live album, two extended plays (EP), 27 singles (including three as featured artist), and five promotional singles. Perry has been certified for 90 million digital singles and 6 million albums in the United States as of August 2017. <P0-S1>  She is also the third best selling digital singles artist in the US according to Recording Industry Association of America (RIAA). <P0-S2>  As of November 2012, Perry has sold over 100 million records globally. <P0-S3>  She currently holds the record for most 5-million-selling singles in the United States, with six of her singles selling over 5 million (in order of release date: "Hot n Cold", "California Gurls", "Firework", "E.T.", "Roar", and "Dark Horse"). <P0-S4>  Perry also holds the record for the most 6-million-selling songs, with three of her songs—"Firework", "Roar", and "Dark Horse"—selling over 6 million copies. <P0-S5>  All three have also received Diamond song certifications from the RIAA, making her the first artist to accomplish such a feat. <SEP> <P1-S0> "Empire State of Mind (Part II) Broken Down" is a song performed by American recording artist Alicia Keys. <P1-S1>  It is an answer song to the "Billboard" Hot 100 number-one hit "Empire State of Mind" by Jay-Z, on which Keys is featured. <P1-S2>  It was only officially released in the United Kingdom as the second single from her 2009 album "The Element of Freedom" although it gained international airplay and download sales. <SEP> <P2-S0> "Empire State of Mind" is a song performed by American rapper Jay-Z and featuring vocals by American singer Alicia Keys that was written by Angela Hunte and Jane't Sewell-Ulepic. <P2-S1>  Produced by Al Shux, Angela Hunte and Jane't Sewell-Ulepic, it was released as the third single from Jay-Z's 11th studio album, "The Blueprint 3" (2009), by his Roc Nation label in October 2009. <P2-S2>  The song was written as a tribute to both artists' hometown, New York City, and features music samples of "Love on a Two-Way Street" performed by The Moments. <P2-S3>  The following month they submitted the song to Jay-Z's Roc Nation, whose reviews were a discouragement. <P2-S4>  Following an incident that Hunte and Sewell-Ulepic describe as an omen, they took the suggestion of an associate of EMI Music Publishing and resubmitted it to Jay-Z, who kept the "New York" singing part on the hook, changed the verses, and recorded it as a single. <SEP> <P3-S0> "California Gurls" is a song recorded by American singer Katy Perry. <P3-S1>  It served as the lead single for her third studio album, "Teenage Dream" (2010). <P3-S2>  The song features verses from rapper Snoop Dogg. <P3-S3>  Both artists co-wrote the song with Bonnie McKee and its co-producers Dr. Luke and Max Martin, with additional production from Benny Blanco. <P3-S4>  According to Perry, "California Gurls" is an answer song to "Empire State of Mind" (2009), by Jay-Z and Alicia Keys. <P3-S5>  Its midtempo production incorporates disco-pop, and funk-pop with influences of new wave, and electropop. <P3-S6>  Its lyrics are an ode to the state of California, in which both Perry and Snoop Dogg were born and raised.