def best_trade(include, exclude, workload):
    """
    Make the best possible trade of one combination between include and exclude
    to improve the balance of the workload.

    We can understand this as finding the most loaded combination of workers
    and replacing it with the least loaded.
    """
    score = lambda x: sum(workload[i] for i in x)
    outcombo = max(include, key=score)
    incombo = min(exclude, key=score)

    return incombo, outcombo