Rivera Inc. is a publicly traded firm with 200 million shares trading at $ 10 a share and no debt outstanding. The firm announces that it will be borrowing $ 500 million and buying back its own stock. On the announcement, the stock price increases to $ 10.50 a share. If the tax rate for the firm is 40% and the cost of bankruptcy is estimated to be 25% of the unlevered firm value, please estimate the probability of bankruptcy with the additional debt.