```\n/// @dev Allows an owner to confirm a transaction.\n/// @param transactionId Transaction ID.\nfunction confirmTransaction(uint256 transactionId)\n    public\n    ownerExists(msg.sender)\n    transactionExists(transactionId)\n    notConfirmed(transactionId, msg.sender)\n    notFullyConfirmed(transactionId)\n{\n    confirmations[transactionId][msg.sender] = true;\n    emit Confirmation(msg.sender, transactionId);\n    if (isConfirmed(transactionId)) {\n        \_setConfirmationTime(transactionId, block.timestamp);\n    }\n}\n```\n