user: Question: What is the PRR class of the Freight train built in 1967 with a B-B wheel arrangement?
Columns: ['PRR Class', 'Builder’s Model', 'Build date', 'Total produced', 'Wheel arrangement', 'Service', 'Power output']
Types: ['text', 'text', 'text', 'real', 'text', 'text', 'text']
Sample row: ['ES6', 'SW', '1937', 12.0, 'B-B', 'Switcher', 'hp (kW)']
SQL:

assistant: SELECT "PRR Class" FROM "Table" WHERE "Wheel arrangement" = 'B-B' AND "Service" = 'Freight' AND "Build date" = '1967';