Table schema:
CREATE TABLE table_name_9 (effic INTEGER, cmp_att_int VARCHAR, avg_g VARCHAR, gp_gs VARCHAR)

Question: Which Effic is the average one that has an Avg/G larger than 3.7, and a GP-GS of 13, and a Cmp-Att-Int of 318-521-15?
SQL: SELECT AVG(effic) FROM table_name_9 WHERE avg_g > 3.7 AND gp_gs = "13" AND cmp_att_int = "318-521-15"