Question: What singer signed a contract with Def Jam Recordings at age 19 and was mentored by LA Reid and Jay-Z?

<P0-S0> Music of the Sun is the debut studio album by Barbadian singer Rihanna. <P0-S1>  It was released on August 30, 2005 in the United States through Def Jam Recordings. <P0-S2>  Prior to signing with Def Jam, Rihanna was discovered by record producer Evan Rogers in Barbados, who helped Rihanna record demo tapes to send out to several record labels. <P0-S3>  Jay-Z, the former chief executive officer (CEO) and president of Def Jam, was given Rihanna's demo by Jay Brown, his A&R at Def Jam, and invited her to audition for the label after hearing what turned out to be her first single, "Pon de Replay". <P0-S4>  She auditioned for Jay-Z and L.A. Reid, the former CEO and president of record label group The Island Def Jam Music Group, and was signed on the spot to prevent her from signing with another record label. <SEP> <P1-S0> Ameriie Mi Marie Rogers (born January 12, 1980), known professionally as Amerie (currently Ameriie), is an American singer, songwriter, author, actress and record producer. <P1-S1>  She debuted in 2002 with her highly acclaimed debut album "All I Have". <P1-S2>  In 2003, she helped develop the BET original series "The Center", which she also hosted, and, during her run as host, accumulated the highest ratings ever for any show in its time slot. <P1-S3>  Amerie's time on the series was short-lived due to her landing a starring role in the 2004 film "First Daughter", alongside Katie Holmes, Marc Blucas, and Michael Keaton. <P1-S4>  In 2005, Amerie released her sophomore album "Touch", which included her biggest hit to date, "1 Thing". <P1-S5>  The song and the album earned her two Grammy nominations and gained her crossover recognition. <P1-S6>  Her third album, "Because I Love It", achieved moderate international success in 2007, although it was not released in North America and she was subsequently bought out of her Sony contract by LA Reid Columbia Records' roster. <P1-S7>  Ameriie released her fourth studio album, "In Love & War", in 2009 on Island Def Jam. <SEP> <P2-S0> Christine Flores (born September 26, 1981), better known as Christina Milian ( ), is an American singer, songwriter and actress. <P2-S1>  At the age of 19, Milian signed a contract with Def Jam. <P2-S2>  In 2001, Milian released her self-titled debut album, which featured the singles "AM to PM" and "When You Look at Me"; "AM to PM" charted within the Top 40 of the U.S. "Billboard" Hot 100 and both peaked in the top three on the UK Singles Chart. <P2-S3>  In 2004, Milian released her second studio album "It's About Time", which provided her first major U.S. hit, "Dip It Low", which reached number five on the U.S. "Billboard" chart. " <P2-S4> Whatever U Want" was released as the album's second single. <P2-S5>  Both singles charted within the Top 10 of the UK chart. <SEP> <P3-S0> So Amazin' is the third studio album by American singer Christina Milian. <P3-S1>  The album, her first studio release since 2004's "It's About Time", was released by Island Records on May 16, 2006 in the United States. <P3-S2>  Unlike previous records, which had contributions from many producers, Milian wrote and produced "So Amazin"' primarily with hip hop producers Cool & Dre. <P3-S3>  During production, Milian was mentored by L.A. Reid and executive producer Jay-Z of Def Jam Recordings.