Question: What is the fare to Kalamazoo during the time frame when Saginaw's was $481.39?
Schema: create table table_1637981_7 (kalamazoo__azo_ varchar, saginaw__mbs_ varchar, PRIMARY KEY (kalamazoo__azo_))
SQL: select kalamazoo__azo_ from table_1637981_7 where saginaw__mbs_ = "$481.39"