function coldStore(uint _amount) external onlyOwner {
        houseKeeping();
        require(_amount > 0 && this.balance >= (investBalance * 9 / 10) + walletBalance + _amount);
        if(investBalance >= investBalanceGot / 2){ 
            require((_amount <= this.balance / 400) && coldStoreLast + 60 * 60 * 24 * 7 <= block.timestamp);
        }
        msg.sender.transfer(_amount);
        coldStoreLast = block.timestamp;
    }