user: Question: What is the earliest Year commissioned wiht an Average annual output greater than 58 and Installed capacity of 20?
Columns: ['Name', 'Year commissioned', 'Gross head (metres)', 'Installed capacity (megawatts)', 'Average annual output (million KWh)']
Types: ['text', 'real', 'real', 'real', 'real']
Sample row: ['Deanie', 1963.0, 113.0, 38.0, 92.0]
SQL:

assistant: SELECT MIN("Year commissioned") FROM "Table" WHERE "Average annual output (million KWh)" > 58.0 AND "Installed capacity (megawatts)" = 20.0;