human
Considering the provided database schema and associated query, produce SQL code to retrieve the answer to the query. 
###Database Schema: Name, Year commissioned, Gross head (metres), Installed capacity (megawatts), Average annual output (million KWh)
###Question: What is the earliest Year commissioned wiht an Average annual output greater than 58 and Installed capacity of 20?
gpt
SELECT MIN Year commissioned FROM table WHERE Average annual output (million KWh) > 58 AND Installed capacity (megawatts) = 20