function payoutInvestor(uint256 investorId) public {
        require (investorId < investorsCount && investorsEarned[investorId] > 0);

        uint256 paymentAmount = investorsEarned[investorId] * toGwei; 
        feeAmount -= investorsEarned[investorId];
        investorsEarned[investorId] = 0;

        bool isSuccess = investorsAddress[investorId].send(paymentAmount);

        emit EvInvestorPayout(curIteration, bankAmount, investorId, paymentAmount, isSuccess);
    }