user: Question: Which Commercial Operation has both a Gross Capacity of 417 MW and an Electricity Grid 27.12.1971?
Columns: ['Unit', 'Reactortype', 'Net capacity', 'Gross capacity', 'Construction started', 'Electricity Grid', 'Commercial Operation', 'Shutdown']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Novovoronezh-1', 'VVER-210 (prototype)', '197 MW', '210 MW', '01.07.1957', '30.09.1964', '31.12.1964', '16.02.1988']
SQL:

assistant: SELECT "Commercial Operation" FROM "Table" WHERE "Gross capacity" = '417 MW' AND "Electricity Grid" = '27.12.1971';