Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_name_20 (tujia_population INTEGER, prefecture VARCHAR, county VARCHAR)
### Question:
What is the sum of Tujia population with the Zhangjiajie prefecture in Sangzhi county?
### Answer:
SELECT SUM(tujia_population) FROM table_name_20 WHERE prefecture = "zhangjiajie" AND county = "sangzhi"