Table: t_1938_british_empire_games
Columns: rank
nation
gold
silver
bronze
total

Question: What is the most silver medals won among nations that won more than 40 medals total, less than 25 of them being gold, and more than 15 of them being bronze?
SQL: SELECT MAX("silver") FROM t_1938_british_empire_games WHERE "total" > 40 AND "gold" < 25 AND "bronze" > 15