A more thorough explanation:

Definition: Mandatory power refers to a type of power that must be exercised as instructed, without any discretion. It is a legal right or authorization to act or not act, which allows a person or organization to alter legal relations.

Example: A trustee is given a mandatory power to distribute the assets of a trust to the beneficiaries according to the terms of the trust. The trustee must follow the instructions given in the trust document and has no discretion to act otherwise.

This example illustrates the definition of mandatory power as the trustee is required to act in a specific manner and has no authority to make decisions on their own. They must follow the instructions given to them and cannot exercise any discretion.