## Complete the Open Function In this video, we will complete the `open` function to create a leveraged position using a flash loan. To start, we will pull the collateral from the message sender as: ```solidity IERC20(params.collateral).transferFrom(msg.sender, address(this), params.colAmount) ``` Next, we will initiate a flash loan using the helper function in `AaveHelper.sol`, which takes in the token, amount, and data as inputs: ```solidity flashLoan( { token: params.coin, amount: params.coinAmount, data: abi.encode( FlashLoanData( { coin: params.coin, collateral: params.collateral, open: true, caller: msg.sender, colAmount: params.colAmount, swap: params.swap } ) ) } ); ``` After initiating a flash loan to create a leveraged position, we will make sure that the health factor is greater than a number that the user specifies with: ```solidity require( getHealthFactor(address(this)) >= params.minHealthFactor, "health factor < min" ); ``` Next, we will implement `flashLoanCallback` to perform our logic. We will start with borrowing with: ```solidity uint256 repayAmount = amount + fee; ``` Then, we will initialize coin and collateral as `IERC20` as: ```solidity IERC20 coin = IERC20(data.coin); IERC20 collateral = IERC20(data.collateral); ``` Next, we can finish the process by approving Aave for `repayAmount` as: ```solidity coin.approve(address(pool), repayAmount); ``` We will take the collateral that we bought and add the collateral that the user specified initially: ```solidity uint256 colAmount = data.colAmount + colAmountOut; ``` Next, we will supply the collateral and pass it as collateral to Aave as: ```solidity supply(address(collateral), colAmount); ``` Then, we borrow the stable coin for the flash loan amount plus fee as: ```solidity borrow(address(coin), repayAmount); ``` To test that the code compiles we run: ```bash forge build ```