func: 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) );
      }