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contracts...L1Contract.sol

pragma solidity ^0.6.11;

import "./ArbSys.sol";
import "./IInbox.sol";

contract L1Contract {
    address constant ARBSYS_ADDR = address(0x0000000000000000000000000000000000000064);
    address inbox;
    
    event WithdrawalCreated(uint256 amount, uint256 indexed id);
    
    function withdrawEthFromL2(
        uint256 _amountToWithdraw,
        uint256 maxSubmissionCost,
        uint256 maxGas,
        uint256 gasPriceBid,
        address refundAddr
    ) external returns (uint256 id) {
        // we want the L1 to L2 tx to trigger the Arbsys precompile
        // then create a L2 to L1 transaction transferring `_amountToWithdraw`
        bytes memory l1ToL2Calldata = abi.encodeWithSelector(
            ArbSys.sendTxToL1.selector,
            address(this),
            L1Contract.receiveETH.selector
        );

        id = IInbox(inbox).createRetryableTicketNoRefundAliasRewrite(
            ARBSYS_ADDR,
            _amountToWithdraw,
            maxSubmissionCost,
            refundAddr,
            refundAddr,
            maxGas,
            gasPriceBid,
            l1ToL2Calldata
        );
        emit WithdrawalCreated(_amountToWithdraw, id);
        return id;
    }
    
    function receiveETH() external payable {}
}