Question: Name the part which is most profitable.
SQL: SELECT T.p_name FROM ( SELECT T3.p_name , T2.l_extendedprice * (1 - T2.l_discount) - T1.ps_supplycost * T2.l_quantity AS num FROM partsupp AS T1 INNER JOIN lineitem AS T2 ON T1.ps_suppkey = T2.l_suppkey INNER JOIN part AS T3 ON T1.ps_partkey = T3.p_partkey ) AS T ORDER BY T.num DESC LIMIT 1