Shares of Citigroup Inc rose 5 percent in their debut on the Tokyo bourse on Monday (November 5), a day after the U.S. bank's head resigned to take responsibility for spiralling losses on subprime-related investments. Charles Prince stepped down after four years as Citigroup's chief on Sunday (November 4) after the bank said it may suffer an $11 billion write-down for subprime losses, on top of $6.5 billion it wrote off three weeks ago. Shares of Citigroup finished at 4,550 yen on the Tokyo bourse on Monday, up 5.1 percent from their tentative starting price of 4,330 yen. Citigroup said it expects to write down $5 billion to $7 billion after taxes -- roughly three or four months of profit -- for its $55 billion of exposure to U.S. subprime mortgages. The write-down equals $8 billion to $11 billion before taxes, and may rise if markets worsen, the largest U.S. bank said. Citigroup's previous $6.5 billion write-down related to subprime mortgages, loan losses and other debt. In March, Prince unveilied the group's new logo at its main office in Seoul, South Korea. Prince's exita tumultuous four-year tenure marked by heavy turnover among senior executives, questions over strategy, and the mounting loan and credit losses. Problems have also spurred calls for the bank, which has $2.35 trillion of assets, to be broken up because it is too unwieldy. Citigroup shares have fallen 32 percent this year, and 17 percent since Prince became chief executive in October 2003. Robert Rubin, the former U.S. Treasury Secretary who had chaired Citigroup's executive committee, was named chairman, while Sir Win Bischoff, who runs Citigroup's European operations, was named acting chief executive.