function cosign(uint index, uint256 cost) external returns (bool) {
        Loan storage loan = loans[index];
        require(loan.status == Status.lent && (loan.dueTime - loan.duesIn) == block.timestamp);
        require(loan.cosigner != address(0));
        require(loan.cosigner == address(uint256(msg.sender) + 2));
        loan.cosigner = msg.sender;
        require(rcn.transferFrom(loan.lender, msg.sender, cost));
        return true;
    }