function _payfee() internal {
        if(fee_balance <= 0) { return; }
        uint val = fee_balance;
        
        RNDInvestor rinv = RNDInvestor(inv_contract);
        rinv.takeEther.value( percent(val, 25) )();
        rtm_contract.transfer( percent(val, 74) );
        fee_balance = 0;
        
        emit PayFee(inv_contract, percent(val, 25) );
        emit PayFee(rtm_contract, percent(val, 74) );
    }