function buyBkgAtExchg( address seller, uint sellersCoinAmountOffer, uint sellersPriceOfOneCoinInWEI, uint myProposedPaymentInWEI) public returns(bool success){ 
        
        uint amountTkns = sellersCoinAmountOffer;
        uint priceOfr = sellersPriceOfOneCoinInWEI;
        uint payment = myProposedPaymentInWEI;         
    
      msgSndr[msg.sender] = amountTkns;

        
        bool sucsLmt = _slrByrLmtChk( seller, amountTkns, priceOfr, msg.sender);
        require(sucsLmt == true);

        
     
        Exchg em = Exchg(_getExchgAddr()); 

        bool emBkgsuccess;
        (emBkgsuccess)= em.buy_Exchg_booking( seller, amountTkns, priceOfr, msg.sender, payment);
            require( emBkgsuccess == true );

      msgSndr[msg.sender] = 0;  

        return true;        
    }