Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| FOURCC | DX 10 Name | Description | Alpha premultiplied? | Compression ratio | Texture Type |
| --- | --- | --- | --- | --- | --- |
| DXT1 | BC1 | 1-bit Alpha / Opaque | N/A | 6:1(for 24 bit source image) | Simple non-alpha |
| DXT2 | (none) | Explicit alpha | Yes | 4:1 | Sharp alpha |
| DXT3 | BC2 | Explicit alpha | No | 4:1 | Sharp alpha |
| DXT4 | (none) | Interpolated alpha | Yes | 4:1 | Gradient alpha |
| DXT5 | BC3 | Interpolated alpha | No | 4:1 | Gradient alpha |
Question:
Which Compression ratio has a (none) DX 10 Name and a FOURCC of dxt4?
Answer:
4:1