How many millions of U.S. viewers watched the episode directed by Allison Liddi-Brown? 
CREATE TABLE table_18102421_2 (us_viewers__millions_ VARCHAR, directed_by VARCHAR)
SELECT us_viewers__millions_ FROM table_18102421_2 WHERE directed_by = "Allison Liddi-Brown"
<s>[INST] Write mssql query to answer the following question given the database schema. Schema: CREATE TABLE table_18102421_2 (us_viewers__millions_ VARCHAR, directed_by VARCHAR) Question: How many millions of U.S. viewers watched the episode directed by Allison Liddi-Brown?  [/INST] SELECT us_viewers__millions_ FROM table_18102421_2 WHERE directed_by = "Allison Liddi-Brown" </s>