A state Superior Court judge said today he expects to rule at the end of November in a multi-million dollar case challenging the constitutionality of the states bank tax system. Superior Court Judge Fred S. Silverman gave his timeframe for the much-anticipated decision following arguments in Wilmington by lawyers for Lehman Bros. and the state. Lehman Bros. has sued the state, claiming that Delawares bank tax system is unconstitutional. The New York investment firm claims Delaware violated the U.S. Constitution by taxing all of the income of a subsidiary, Wilmington-based Lehman Brothers Bank FSB. The state contends that its system is constitutional and that Lehman actually owes Delaware more than $12 million in back taxes. Lehman is appealing an earlier administrative ruling by state Bank Commissioner Robert A.