question: What is the date of death of Margaret De Stafford's mother?
context: [["Edmund Stafford, 1st Baron Stafford", ["Edmund de Stafford, 1st Baron Stafford was the son of Nicholas de Stafford, who was summoned to parliament by writ on 6 February 1299 by King Edward I."]], ["Robert de Stafford", ["Robert de Stafford( known also as Robert of Tosny and Robert de Toeni)( 1039 \u2013 c. 1100) was a Norman nobleman, the builder of Stafford Castle in England.", "He is generally said to have been a son of Roger I of Tosny; primary evidence is lacking to determine his parentage, according to Cawley.", "Cawley notes that Robert de Stafford is connected to the Tosny family through a charter( not dated) under which\" Robertus de Stafford\" confirmed donations to Wotton Wawen Abbey, Warwickshire by\" avus meus Robertus de Toenio et pater meus Nicolaus de Stafford.\"", "Also\" Robertus de Staffordia et Robertus filius meus et h\u00e6res\" confirmed donations of property to Evesham Monastery by\" Rodbertus avus meus ... et pater meus Nicholaus\" by undated charter.", "He held a large number of lordships in the Domesday Survey, a high proportion lying in Staffordshire.", "They included Barlaston and Bradley in Staffordshire and part of Duns Tew in Oxfordshire.", "Robert de Stafford was buried in Evesham Abbey."]], ["Katherine de Stafford", ["Katherine de Stafford, Countess of Suffolk( born around 1376 \u2013 8 April 1419) was a daughter of Hugh de Stafford, 2nd Earl of Stafford and his wife Philippa de Beauchamp.", "By her marriage to Michael de la Pole, 2nd Earl of Suffolk, she became known as the Countess of Suffolk."]], ["Hugh Stafford, 2nd Earl of Stafford", ["Hugh de Stafford, 2nd Earl of Stafford, KG( c. 1342 \u2013 16 October 1386) was an English nobleman."]], ["Philippa de Beauchamp", ["Philippa de Beauchamp (before 1344-6 April 1386) was the daughter of Thomas de Beauchamp, 11th Earl of Warwick and Katherine Mortimer.", "On or before 1 March 1350 she married Hugh de Stafford, 2nd Earl of Stafford, son of Ralph de Stafford,", "1st Earl of Stafford and Margaret Audley, Baroness Audley.", "Philippa and Hugh had seven children."]], ["John Sutton III", ["Sir John de Sutton III( 1339 \u2013 c. 1370) was the 2nd Baron Sutton of Dudley and heir of Dudley Castle.", "He was the son of Sir John de Sutton II, the first Lord of Dudley, and Isabella de Cherleton.", "John III married twice, with the first on 25 December 1357 to Katherine de Stafford( 1340/ 8 \u2013 December 1361), daughter of Ralph de Stafford, 1st Earl of Stafford and Margaret de Audley, 2nd Baroness Audley.", "After 1361, he married secondly to Joan, daughter of Sir John de Clinton of Coleshill.", "By Katherine, Sir John de Sutton IV became successor."]], ["Margaret de Loveyne", ["Margaret de Loveyne( died May 1408) was a daughter of Sir Nicholas Loveyne and his second wife Margaret de Vere.", "She inherited extensive property and her second husband was High Sheriff of Surrey and Sussex."]], ["Margaret de Stafford", ["Margaret Stafford (born c. 1364; died 9 June 1396) was the daughter of Hugh de Stafford, 2nd Earl of Stafford, and Philippa de Beauchamp.", "She was the first wife of Ralph Neville, 1st Earl of Westmorland, and the grandmother of the 2nd Earl."]], ["Margaret De Patta", ["Margaret De Patta(\" n\u00e9e\" Strong; 1903 \u2013 1964) was born in Tacoma, Washington, and grew up in San Diego, California.", "She died in Oakland, California.", "She was an American jewelry designer active in the mid-century jewelry movement.", "Her innovative jewelry was influenced by the\" Bauhaus school, constructivism, and democratic ideals\".", "Her work is collected in many major museums including the Smithsonian American Art Museum, the Los Angeles County Museum of Art, and the Oakland Museum of California.", "The first major retrospective of her work,\" Space- Light- Structure: The Jewelry of Margaret De Patta,\" opened at the Museum of Arts and Design in 2012.", "The Velvet da Vinci gallery in San Francisco showed some of her works in\" The De Patta Project: New Jewelry Made With Old Stones Acquired from the Estate of Margaret De Patta( 1903- 1964).\""]], ["Theodred II (Bishop of Elmham)", ["Theodred II was a medieval Bishop of Elmham.", "The date of Theodred's consecration unknown, but the date of his death was sometime between 995 and 997."]]]
supporting_facts: [["Margaret de Stafford", 0], ["Philippa de Beauchamp", 0]]
evidences: [["Margaret Stafford", "mother", "Philippa de Beauchamp"], ["Philippa de Beauchamp", "date of death", "6 April 1386"]]
answer: 6 April 1386