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:
| Ship Name | In Service | Project Number | Type | Class | Comments |
| --- | --- | --- | --- | --- | --- |
| Lenin | 1959 | 92M | Icebreaker | — | Decommissioned 1989. Museum ship. |
| Arktika | 1975 | 1052-1 | Icebreaker | Arktika | Not operational. |
| Sibir | 1977 | 1052-2 | Icebreaker | Arktika | Defueled and not operational since 1993. |
| Rossiya | 1985 | 10521-1 | Icebreaker | Arktika |  |
| Sevmorput | 1988 | 10081 | Container ship | — | Has ice-breaking bow |
| Taymyr | 1989 | 10580-1 | River icebreaker | Taymyr |  |
| Sovetskiy Soyuz | 1990 | 10521-2 | Icebreaker | Arktika |  |
| Vaygach | 1990 | 10580-2 | River icebreaker | Taymyr |  |
| Yamal | 1993 | 10521-3 | Icebreaker | Arktika |  |
| 50 Let Pobedy | 2007 | 10521 | Icebreaker | Arktika | Built as Ural, completed in 2007. |
Question:
how many years later was the sibir in service after the lenin?
Answer:
18