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:
| Operators | Named trains | Destination | Year begun | Year discontinued |
| --- | --- | --- | --- | --- |
| Baltimore and Ohio | Capitol Limited | Chicago, Illinois via Washington, D.C. and Pittsburgh, Pennsylvania | 1923 | 1958* |
| Baltimore and Ohio | Metropolitan Special | St. Louis, Missouri via Washington, D.C. and Cincinnati, Ohio | ca. 1920 | 1958* |
| Baltimore and Ohio | National Limited | St. Louis, Missouri via Washington, D.C. and Cincinnati, Ohio | 1925 | 1958* |
| Baltimore and Ohio | Royal Blue | Washington, D.C. | 1890 | 1958 |
| Central Railroad of New Jersey | Blue Comet | Atlantic City, New Jersey | 1929 | 1941 |
| Reading Railroad with the Central Railroad of New Jersey | Crusader | Philadelphia, Pennsylvania | 1937 | 1967 |
| Reading Railroad with the Central Railroad of New Jersey | Harrisburg Special | Harrisburg, Pennsylvania |  |  |
| Reading Railroad with the Central Railroad of New Jersey | Queen of the Valley | Harrisburg, Pennsylvania |  | 1967 |
| Reading Railroad with the Central Railroad of New Jersey | Wall Street | Philadelphia, Pennsylvania |  |  |
| Reading Railroad with the Central Railroad of New Jersey | Williamsporter | Williamsport, Pennsylvania |  |  |
Question:
what is the difference (in years) between when the royal blue began and the year the crusader began?
Answer:
47