Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What's the sum of the population for the place simplified 上杭县 with an area smaller than 2,879?

### Inputs:
table_name: table, columns: ['English Name', 'Simplified', 'Traditional', 'Pinyin', 'Hakka', 'Area', 'Population', 'Density']

### Response:
SELECT SUM Population FROM table WHERE Simplified = 上杭县 AND Area < 2,879