def concrete_contributions(A_compression, lever_arm, fcd, alpha_cc=1.0):
    """
    Return the contribution from concrete to force and moment capacity of the
    section.

    Parameters
    ----------
    A_compr : number or numpy.ndarray
        Compression areas for each considered location of the neutral axis.
    lever_arm : number
        Lever arm between centroid of gross uncracked section and centroid
        of compression block. Can be negative depending on coordinate system.
    fcd : number
        Design concrete strength
    alpha_cc : number, optional
        Coefficient taking into account long term effects on the
        compressive strength of concrete and unfavorable effects from
        the way loads may be applied. Defaults to 1.0.
        Formula: fcd = alpha_cc * fck / gamma_c

    Returns
    -------
    Fc : number or numpy.ndarray
        Concrete force for each considered location of the neutral axis
    Mc : number or numpy.ndarray
        Concrete moment for each considered location of the neutral axis

    Assumptions:
        * Centroid of uncracked cross section is located at (0, 0)
    """
    Fc = -alpha_cc * fcd * A_compression / 1000
    Mc = Fc * lever_arm / 1000
    return Fc, Mc
