user: Question: What's the sum of the population for the place simplified 上杭县 with an area smaller than 2879?
Columns: ['English Name', 'Simplified', 'Traditional', 'Pinyin', 'Hakka', 'Area', 'Population', 'Density']
Types: ['text', 'text', 'text', 'text', 'text', 'real', 'real', 'real']
Sample row: ['Xinluo District', '新罗区', '新羅區', 'Xīnluó Qū', 'Sîn-lò-khî', 2685.0, 662429.0, 247.0]
SQL:

assistant: SELECT SUM("Population") FROM "Table" WHERE "Simplified" = '上杭县' AND "Area" < 2879.0;