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:
| Speed [km/h (mph)] | Train | Type | Location | Date | Comments |
| --- | --- | --- | --- | --- | --- |
| 504 (313.2) | ML-500 | Maglev | Miyazaki Maglev Test Track | 12 December 1979 |  |
| 517 (321.2) | ML-500 | Maglev | Miyazaki Maglev Test Track | 21 December 1979 |  |
| 352.4 (219.0) | MLU001 | Maglev | Miyazaki Maglev Test Track | January 1986 | Three-car train set |
| 405.3 (251.8) | MLU001 | Maglev | Miyazaki Maglev Test Track | January 1987 | Two-car train set |
| 431 (267.8) | MLU002N | Maglev | Miyazaki Maglev Test Track | February 1994 | Single-car |
| 550 (341.8) | MLX01 | Maglev | Yamanashi Maglev Test Line | 24 December 1997 | Three-car train set |
| 548 (340.5) | MLX01 | Maglev | Yamanashi Maglev Test Line | 18 March 1999 | Five-car train set |
Question:
how many cars were in the set for the december 24, 1997 record?
Answer:
3