def serverUtilisation(arrival_rate: float, departure_rate: float) -> float:
    """ Calculate the expected server Utilisation of the system with the given
    parameters.

    Params:
        - arrival_rate: The exponential mean of arrival for the clients
        - departure_rate: the exponential mean of the departure of the clients

    Returns:
        - float: Value representing the server utilisation value

    """
    return arrival_rate/departure_rate