def cpm(total_cost, total_recipients):
    """Return the CPM (or Cost per Mille) based on the marketing cost per 1000 customers.

    Args:
        total_cost (float): Total cost of marketing.
        total_recipients (int): Total number of marketing recipients.

    Returns:
        cpm (float) as total cost of marketing per 1000 customers.
    """

    return (total_cost / total_recipients) * 1000