Company A announces that it intends to acquire Company B. After the announcement, the share price of Company A is 60 yuan, and the share price of Company B rises by 5 yuan. 30 yuan, A has an 80% chance of evaluating success, and it takes a month. Usually, the annualized rate of return is estimated to be up to 20%, A certain A may enter the market, what is the minimum exchange rate for A certain A to enter the market? Another example A adopts arbitrage method to enter the market, how to trade?