Final answer:
The decision about the cleanup must be agreed upon unanimously by the task force, meaning it follows a unanimity rule, where all members must agree on the outcome.
Step-by-step explanation:
When making the decision about the cleanup, the task force decides that all decisions must be agreed upon unanimously. In other words, the decision would be made by a unanimity rule. This is the most extreme form of supermajority, which requires that all members of a decision-making body must agree on a specific outcome. In contexts such as jury trials in the United States, Australia, and Ireland, a unanimous decision is necessary for a defendant to be found guilty. This reflects the principle that the costs of a wrong decision, or conformity costs, are considered to be too high. On the other hand, when unanimity is required for group decisions on less critical matters, it may lead to high transaction costs, as reaching unanimous agreement can take considerable time and effort.