On what surface did they play the match in the week of October 21?
CREATE TABLE table_name_27 (surface VARCHAR, week VARCHAR)
SELECT surface FROM table_name_27 WHERE week = "october 21"
<s>[INST] Write mssql query to answer the following question given the database schema. Schema: CREATE TABLE table_name_27 (surface VARCHAR, week VARCHAR) Question: On what surface did they play the match in the week of October 21? [/INST] SELECT surface FROM table_name_27 WHERE week = "october 21" </s>