How to evaluate fair value price for a stock (i.e., bank) for an acquisition scenario

If I believe that a publicly traded bank may end up being acquired by another firm, how would I go about figuring out a fair price for its shares? Is there a risk that a bank may be acquired for less than its current share price? Credit Suisse doesn't count here. Assuming that a bank is fundamentally strong and the overall sentiment for the bank is bullish in the next few years, is it safe to assume that a all in purchase of the bank would be higher than the current share price? Would appreciate any insight you may have and some prior examples.