def holling_type_0(X,idx_A,coefficient):
    """ linear response with respect to *destination/predator* compartment
    
    For examples see:
    `Examples <https://gist.github.com/465b/cce390f58d64d70613a593c8038d4dc6>`_

    Parameters
    ----------
    X : np.array
        containing the current state of the contained quantity of each 
        compartment
    idx_A : integer
        index of the element representing the destination/predator compartment
    idx_B : integer
        index of the element representing the origin/pray compartment
    coefficient : float
        governs the slope of the linear response

    Returns
    -------
    df : float
        change in the origin and destitnation compartment. Calculated by
        coefficient*destination_compartment
    
    """
    
    A = X[idx_A] # quantity of the linearly dependant compartment
    df = coefficient*A

    return df