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

### Instruction:
For all countries with 7 bronze medals and a total number of medals less than 13, what's the sum of silver medals?

### Inputs:
table_name: table, columns: ['Rank', 'Nation', 'Gold', 'Silver', 'Bronze', 'Total']

### Response:
SELECT SUM Silver FROM table WHERE Bronze = 7 AND Total < 13