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:
| Number | Builder | Type | Date | Length | Notes |
| --- | --- | --- | --- | --- | --- |
| 51 | American Car Company | Motor | 1904 | 47'9" | retired 1933 |
| 53 | American Car Company | Motor | 1904 | 47'9" | retired 1933 |
| 55 | American Car Company | Motor | 1904 | 47'9" | became inspection car in 1932 retired 1941 |
| 57 | American Car Company | Motor | 1904 | 47'9" | became inspection car in 1932 retired 1941 |
| 59 | W. L. Holman Car Company | Motor | 1904 | 44' | retired 1932 |
| 61 | W. L. Holman Car Company | Motor | 1904 | 44' | retired 1932 |
| 63 | W. L. Holman Car Company | Motor | 1904 | 44' | retired 1932 preserved Western Railway Museum |
| 65 | W. L. Holman Car Company | Motor | 1904 | 44' | retired 1932 |
| 67 | W. L. Holman Car Company | Motor | 1904 | 44' | retired 1932 |
| 69 | W. L. Holman Car Company | Motor | 1904 | 44' | converted to express trailer in 1919 retired 1932 |
| 71 | W. L. Holman Car Company | Trailer | 1905 | 44' | retired 1929 |
| 73 | W. L. Holman Car Company | Trailer | 1905 | 44' | retired 1929 |
| 01 | W. L. Holman Car Company | Express Trailer | 1916 |  | built as #8 express motor demotorized 1917 designated express trailer 1920 retired 1933 |
Question:
what was the number of cars built by american car company?
Answer:
4