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:
| District | Incumbent | Party | First elected | Result | Candidates |
| --- | --- | --- | --- | --- | --- |
| Illinois 3 | Fred E. Busbey | Republican | 1942.0 | Lost re-election Democratic gain | Edward A. Kelly (D) 52.0% Fred E. Busbey (R) 48.0% |
| Illinois 4 | Martin Gorski | Democratic | 1942.0 | Re-elected | Martin Gorski (D) 80.4% Leo J. Kozicki (R) 19.6% |
| Illinois 5 | Adolph J. Sabath | Democratic | 1906.0 | Re-elected | Adolph J. Sabath (D) 76.3% Max Price (R) 23.7% |
| Illinois 12 | Noah M. Mason | Republican | 1936.0 | Re-elected | Noah M. Mason (R) 61.0% Herbert J. Max (D) 39.0% |
| Illinois 13 | Leo E. Allen | Republican | 1932.0 | Re-elected | Leo E. Allen (R) 70.0% Garett J. Schutt (D) 30.0% |
| Illinois 16 | Everett Dirksen | Republican | 1932.0 | Re-elected | Everett Dirksen (R) 59.0% M. R. Clark (D) 41.0% |
| Illinois 18 | Jessie Sumner | Republican | 1938.0 | Re-elected | Jessie Sumner (R) 56.9% Carl B. Jewell (D) 43.1% |
| Illinois 20 | Sid Simpson | Republican | 1942.0 | Re-elected | Sid Simpson (R) 55.6% Don Irving (D) 44.4% |
| Illinois 22 | Calvin D. Johnson | Republican | 1942.0 | Lost re-election Democratic gain | Melvin Price (D) 50.8% Calvin D. Johnson (R) 49.2% |
Question:
Who were the candidates when Sid Simpson was the incumbent?
Answer:
Sid Simpson (R) 55.6% Don Irving (D) 44.4%