CREATE TABLE table_39144 ("FOURCC" TEXT, "DX 10 Name" TEXT, "Description" TEXT, "Alpha premultiplied?" TEXT, "Compression ratio" TEXT, "Texture Type" TEXT)

Which Compression ratio has a (none) DX 10 Name and a FOURCC of dxt4?
SELECT "Compression ratio" FROM table_39144 WHERE "DX 10 Name" = '(none)' AND "FOURCC" = 'dxt4'
SELECT "Compression ratio" FROM "table_39144" WHERE "DX 10 Name" = '(none)' AND "FOURCC" = 'dxt4'