A relevant market refers to a group of firms' products that are closely substitutible for one another and available to consumers in a particular geographic area.

A$.$ False

B$.$ True

When assessing a potential horizontal merger, which of the following changes will raise antitrust concerns with federal enforcement agencies?

A$.$ a combined HHI change exceeding $200$ and a postmerger HHI above $1,000$

B$.$ a combined HHI change exceeding $150$ and a postmerger HHI above $1,500$

C$.$ a combined HHI change exceeding $50$ and a postmerger HHI above $2,000$

D$.$ a combined HHI change exceeding $100$ and a postmerger HHI above $2,500$