Question: What is the date of death of Siemowit V Of Masovia's mother?

Knowledge 1: Siemowit V of Masovia
Siemowit V of Rawa (pl: "Siemowit V rawski"; 1389 - 17 February 1442), was a Polish prince member of the House of Piast from the Masovian branch.He was a Duke of Rawa Mazowiecka, Płock, Sochaczew, Gostynin, Płońsk, Wizna and Belz during 1426-1434 jointly with his brothers, and after the division of the paternal inheritance between him and his brothers in 1434, sole ruler over Rawa Mazowiecka, Gostynin and Sochaczew.He was the eldest son of Siemowit IV, Duke of Masovia and Alexandra of Lithuania, daughter of Algirdas. [SEP] Knowledge 2: Alexandra of Lithuania
Alexandra (died 20 April 1434 in Płock) was the youngest daughter of Algirdas, Grand Duke of Lithuania, and his second wife, Uliana of Tver.Though Alexandra's exact date of birth is not known, it is thought that she was born in the late 1360s or early 1370s.In 1387, she married Siemowit IV, Duke of Masovia, and bore him thirteen children.
Knowledge 1: Siemowit V of Masovia
Siemowit V of Rawa (pl: "Siemowit V rawski"; 1389 - 17 February 1442), was a Polish prince member of the House of Piast from the Masovian branch.He was a Duke of Rawa Mazowiecka, Płock, Sochaczew, Gostynin, Płońsk, Wizna and Belz during 1426-1434 jointly with his brothers, and after the division of the paternal inheritance between him and his brothers in 1434, sole ruler over Rawa Mazowiecka, Gostynin and Sochaczew.He was the eldest son of Siemowit IV, Duke of Masovia and Alexandra of Lithuania, daughter of Algirdas. [SEP] Knowledge 2: Sophia of Masovia
Sophia of Masovia( 1497/1498- before 11 March 1543) was a Princess of Masovia, daughter of Konrad III Rudy, Duke of Masovia and his wife Anna Radziwiłł.She was a member of the House of Piast.On 17 September 1520 in Warsaw, Sophia was married by proxy to Stephen VII Báthory.On 17 January 1521, Sophia and her entourage went to Hungary, where in February there was a formal marriage.The couple had three children:Anna, Stephen and Klara; however, other sources claim that Klara was the couple's only child.Klara was engaged to Carl, Duke of Münsterberg, but died in 1535, before the marriage took place.After the death of Stephen in 1530, Sophia was married to Croatian magnate Louis Pekry.Sophia's second marriage was childless.She then died sometime before 11 March 1543.Sophia had three siblings: Stanislaus I of Masovia, Janusz III of Masovia and Anna of Masovia, both her brothers died childless and so Anna and Sophia were the last Masovian Piasts.Soon after Janusz's death, the Duchy of Masovia was annexed into the kingdom of Poland, despite resistance from some of the Masovian nobility.They tried to retain their independence and argued that the Duchy should be inherited by the female relatives( such as Anna or Sophia).The Polish king refused to recognize their demands.Anna was made titular Duchess of Masovia.
Knowledge 1: Siemowit V of Masovia
Siemowit V of Rawa (pl: "Siemowit V rawski"; 1389 - 17 February 1442), was a Polish prince member of the House of Piast from the Masovian branch.He was a Duke of Rawa Mazowiecka, Płock, Sochaczew, Gostynin, Płońsk, Wizna and Belz during 1426-1434 jointly with his brothers, and after the division of the paternal inheritance between him and his brothers in 1434, sole ruler over Rawa Mazowiecka, Gostynin and Sochaczew.He was the eldest son of Siemowit IV, Duke of Masovia and Alexandra of Lithuania, daughter of Algirdas. [SEP] Knowledge 2: Hedwig of Masovia
Hedwig of Masovia( ca. 1392 – after 19 February 1439), was a Polish princess, member of the House of Piast in the Masovian branch.She was the eldest daughter of Siemowit IV, Duke of Masovia and Alexandra, a daughter of Algirdas, Grand Duke of Lithuania and sister of King Władysław II Jagiełło of Poland.

Answer: 20 April 1434