The FDIC expects the cost of resolving failed banks to grow to about $100 billion over the next four years.The agency mandated last year that banks prepay about $45 billion in premiums, for 2010 through 2012, to replenish the insurance fund. Depositors' money ¿ insured up to $250,000 per account ¿ is not at risk, with the FDIC backed by the government. Apart from the fund, the FDIC has about $66 billion in cash and securities available in reserve to cover losses at failed banks. ___ Augstums reported from Charlotte. Gordon reported from Washington, D.C.