Unless of course it's to be assumed that government intervention means that banks that would have been bankrupt are no longer bankrupt. In which case the probability will be 0.5 - Pr(x < number of banks that go bankrupt < n). I will let you consult your class notes or textbook on how to calculate the second term.
(Ahhh banks. You've got to love them .... Privatise profit, socialise risk).