Final answer:
A firm's announcement to buy a fixed number of shares at a specific price is called a tender offer.
Step-by-step explanation:
When a firm announces to all of its stockholders that it is willing to buy a fixed number of shares at a specific price, it is referred to as a tender offer. A tender offer is a public invitation to shareholders to sell their shares back to the company at a specific price within a certain timeframe. This is a common way for a company to return capital to its shareholders or increase its ownership stake in the company.