# Flash Exercises In this exercise, you'll learn how to liquidate an under-collateralized debt from Aave V3. The starter code for this exercise is provided in `foundry/src/exercises/Flash.sol` Solution is provided in `foundry/src/solutions/Flash.sol` ## Task 1 - Initiate flash loan ```solidity function flash(address token, uint256 amount) public {} ``` Initiate the flash loan - `token` is the token to borrow - `amount` is the amount to borrow > Hints > > - Call `pool.flashLoanSimple` > - ABI encode `msg.sender` and pass it as input to `params` ## Task 2 - Repay flash loan ```solidity function executeOperation( address asset, uint256 amount, uint256 fee, address initiator, bytes calldata params ) public returns (bool) { // Task 2.1 - Check that msg.sender is the pool contract // Task 2.2 - Check that initiator is this contract // Task 2.3 - Decode caller from params and transfer // flash loan fee from this caller // Task 2.4 - Approve the pool to spend flash loaned amount + fee // Task 2.5 - Return true } ``` Implement the callback function called by Aave. > Hints > > - ABI decode `params` and transfer the flash loan fee from the caller that is encoded into `params` ## Test ```shell forge test --fork-url $FORK_URL --fork-block-number $FORK_BLOCK_NUM --match-path test/Flash.test.sol -vvv ```