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:
| Class | Operator | Number | Year Built | Cars per Set | Unit Numbers. |
| --- | --- | --- | --- | --- | --- |
| Class 253 | BR Western Region | 27.0 | 1975-1977 | 9.0 | 253001-253027 |
| Class 253 | BR Western Region | 13.0 | 1978-1979 | 9.0 | 253028-253040 |
| Class 253 | BR Cross Country | 18.0 | 1981-1982 | 9.0 | 253041-253058 |
| Class 254 | BR Eastern Region BR Scottish Region | 32.0 | 1977-1979 | 10.0 | 254001-254032 |
| Class 254 | BR Eastern Region BR Scottish Region | 4.0 | 1982 | 10.0 | 254033-254037 |
Question:
What year was the class 253 larger than 18 built?
Answer:
1975-1977