def calculate_plane_point(plane, point):
    """Calculates the point on the 3D plane for a point with one value missing

    :param plane: Coefficients of the plane equation (a, b, c, d)
    :param point: 3D point with one value missing (e.g. [None, 1.0, 1.0])
    :return: Valid point on the plane
    """

    a, b, c, d = plane
    x, y, z = point

    if x is None:
        x = -(b*y + c*z + d) / a
    elif y is None:
        y = -(a*x + c*z + d) / b
    elif z is None:
        z = -(a*x + b*y + d) / c

    return [x, y, z]