anti trust?

It is legislation to try and ensure competitiveness between companies.
To stop companies having a monopoly position and to stop companies secretly fixing prices together.

If you want more detail then look on Google, but you do not need more detail for the exam.

For the exam, the most likely relevance is that it could be worth mentioning (in the written comments) if a company is acquiring another company that might be regarded by the courts as allowing them to dominate the market that they are in – then it is something that they would need to take into account when deciding whether or not to acquire the company. The takeover could be stopped by the courts.
(No calculations – just a point for the written part of a question)