To calculate the total cost of hosting three recruiting events, we need to determine the cost per event and then multiply it by the number of events.
Each event charges $100 per hour, and if each event ran for two hours, the cost for each event would be $100/hour * 2 hours = $200.
Now, to find the total cost for three events, we multiply the cost per event by the number of events: $200 * 3 events = $600.
Therefore, the correct answer is c) $600.