user: Question: what is the operator of trains arriving at 13.39 
Columns: ['Departure', 'Going to', 'Calling at', 'Arrival', 'Operator']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['06.40', 'Stamford East', 'Ryhall & Belmesthorpe, Stamford East', '06.50', 'GNR']
SQL:

assistant: SELECT "Operator" FROM "Table" WHERE "Arrival" = '13.39';