Facts:   - rrborn: dae won-yu    - mrborn: tae wŏn-yu    - hanjaborn: 大元瑜    - hangul: 정왕    - mr: chŏng wang    - rr: jeong wang      - hangulborn: 대원유    - hanja: 定王   Based on these bullet points, write a short biography describing the life of jeong of balhae .
Answer:
jeong of balhae -lrb- died 812 ? -rrb--lrb- r. 809 -- 812 ? -rrb-was the seventh king of balhae .he was the son of king gang .little is known of his reign , save that he chose the era name `` yeongdeok '' -lrb- 永德 , `` eternal virtue '' -rrb- .after his death , his brother succeeded him as king hui .