user: Question: what is the road numbers when the class is Z-7?
Columns: ['Railroad (quantity)', 'Class', 'Road numbers', 'Builder', 'Build year']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Clinchfield Railroad (12 new, 6 secondhand)', 'E-1', '650–657', 'ALCO', '1942–1943']
SQL:

assistant: SELECT "Road numbers" FROM "Table" WHERE "Class" = 'Z-7';