This is the result of the process:
Agency is terminated by fulfillment
Step-by-step explanation:
The process that the person is hired for has been completed as they are a broker agent and their work is to make the purchase of the office building possible.
Until the building was to be purchased they had an amount of agency about them but this is not valid as soon as the work is terminated or completed.
So here, the agency is terminated by the fulfillment of the work that was assigned to the broker.
There is no work in the deal remaining to be done so the agency is taken away by default.