human
Considering the provided database schema and associated query, produce SQL code to retrieve the answer to the query. 
###Database Schema: Series #, Season #, Title, Directed by, Written by, Original air date, Prod. code, U.S. viewers (millions)
###Question: What was the production code of the episode directed by Rondell Sheridan? 
gpt
SELECT MAX Prod. code FROM table WHERE Directed by = Rondell Sheridan