user: Question: Which Compression ratio has a (none) DX 10 Name and a FOURCC of DXT4?
Columns: ['FOURCC', 'DX 10 Name', 'Description', 'Alpha premultiplied?', 'Compression ratio', 'Texture Type']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['DXT1', 'BC1', '1-bit Alpha / Opaque', 'N/A', '6:1(for 24 bit source image)', 'Simple non-alpha']
SQL:

assistant: SELECT "Compression ratio" FROM "Table" WHERE "DX 10 Name" = '(none)' AND "FOURCC" = 'DXT4';