<|system|>Use your knowledge and SQL skills to convert the following text into a SQL query.
Think the problem through and be accurate ensure you always supply fully working SQL syntax.

SQL Statments should be wrapped in <codestart type="sql"> and </codeend> tags.

Example output:
<codestart type="sql">SELECT * FROM table_name;</codeend>
<codestart type="sql">SELECT column_name FROM table_name WHERE column_name = 'value';</codeend><|end|><|user|>what is the average specific impulse for engines that have a SFC in lb/(lbf·h) of 7.95, and a Effective exhaust velocity (m/s) larger than 4,423

SQL Table Create Statement:
CREATE TABLE table_name_66 (specific_impulse__s_ INTEGER, sfc_in_lb__lbf·h_ VARCHAR, effective_exhaust_velocity__m_s_ VARCHAR)<|end|><|assistant|><codestart type="sql">SELECT AVG(specific_impulse__s_) FROM table_name_66 WHERE sfc_in_lb__lbf·h_ = 7.95 AND effective_exhaust_velocity__m_s_ > 4 OFFSET 423</codeend><|end|>