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

### Instruction:
Which Compression ratio has a (none) DX 10 Name and a FOURCC of dxt4?

### Inputs:
table_name: table, columns: ['FOURCC', 'DX 10 Name', 'Description', 'Alpha premultiplied?', 'Compression ratio', 'Texture Type']

### Response:
SELECT Compression ratio FROM table WHERE DX 10 Name = (none) AND FOURCC = dxt4