[jyl]

Not a broker, but - Answer is, there is no general answer. Depends on how the transaction is structured - cash or stock.

Cash - Company B could buy Company A's shares for $6.00/sh cash. In which case post-merger, a former owner of 1 share in Company A simply has $6.00.

Stock - Company B could exchange 0.2 Company B shares for every 1 Company A shares. In which case post-merger, a former owner of 1 share in Company A now has 0.2 Company B shares, which is worth 0.2 x whatever Company B shares are trading at. $8 if Company B's shares are still $40, but that's not guaranteed.

Cash plus stock - can have some combination of the above.

You have to read the details of the deal, which will usually be in the press release.