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

### Instruction:
What is average quantity, when DRG number is 99 011?

### Inputs:
table_name: table, columns: ['Class', 'Railway number(s)', 'DRG number(s)', 'Quantity', 'Year(s) of manufacture', 'Axle arrangement ( UIC ) Bauart']

### Response:
SELECT AVG Quantity FROM table WHERE DRG number(s) = 99 011