def regional_net_costs(region, asset_type, costs, core_lut, strategy, country_parameters):
    """
    Return regional asset costs for only the 'new' assets that have been planned.

    Parameters
    ----------
    region : dict
        The region being assessed and all associated parameters.
    asset_type : string
        Either a regional edge or node asset.
    costs : dict
        All equipment costs.
    core_lut : dict
        Contains the number of existing and required, core and regional assets.
    strategy : dict
        The strategy string controls the strategy variants being tested in the
        model and is defined based on the type of technology generation, core
        and backhaul, and the level of sharing, subsidy, spectrum and tax.
    country_parameters : dict
        All country specific parameters.

    Returns
    -------
    regional_cost : int
        Regional network cost for defined asset type per cell site.

    """
    core = strategy.split('_')[1]

    if asset_type in core_lut.keys():

        combined_key = '{}_{}'.format(region['GID_id'], 'new')

        if combined_key in core_lut[asset_type]:

            if asset_type == 'regional_edge':

                distance_m = core_lut[asset_type][combined_key]
                cost_m = costs['regional_edge']
                cost = int(distance_m * cost_m)

                all_sites = (region['new_mno_sites'] + region['upgraded_mno_sites'])

                if all_sites == 0:
                    return 0
                elif all_sites <= 1:
                    return int(cost * all_sites)
                else:
                    return int(cost / all_sites)

            elif asset_type == 'regional_node':

                regional_nodes = core_lut[asset_type][combined_key]

                cost_each = costs['regional_node_{}'.format(core)]

                regional_node_cost = int(regional_nodes * cost_each)

                all_sites = (region['new_mno_sites'] + region['upgraded_mno_sites'])

                if all_sites == 0:
                    return 0
                elif all_sites <= 1:
                    return int(regional_node_cost * all_sites)
                else:
                    return int(regional_node_cost / all_sites)

                return int(regional_node_cost / all_sites)

            else:
                return 'Did not recognise core asset type'
        else:
            return 0

    return 'Asset name not in lut'