It’s no secret that Bank of America has been hammered by the foreclosure fiasco and the related worries that banks are going to be forced to buy back bad mortgage-backed securities both from Fannie and Freddie — so-called agencies — and from other investors in the so-called “private label” market. It’s a tough issue for investors and analysts to get their arms around. Credit Suisse analyst Moshe Orenbuch takes a crack at it in a note published Tuesday.