Okay, here is the written lesson based on the provided criteria: ### Calling the Exchange Function Let's go over the solution for calling the `exchange` function on the pool contract. First, we need to inspect the interface for the `ITriCrypto` contract. This is found in the `src/interfaces/curve/ITriCrypto.sol` file. ```javascript interface ITriCrypto { function precisions() external view returns (uint256[3] memory); function price_scale(uint256 i) external view returns (uint256); function balances(uint256 i) external view returns (uint256); function get_dy(uint256 i, uint256 j, uint256 dx) external view returns (uint256 dy); function exchange( uint256 i, uint256 j, uint256 dx, uint256 min_dy, bool use_eth, address receiver ) external; function add_liquidity(uint256[3] calldata amounts, uint256 min_lp, bool use_eth, address receiver) external returns(uint256 lp); function remove_liquidity(uint256 amount, uint256[3] calldata min_amounts, bool use_eth, address receiver) external returns(uint256[3] memory); function remove_liquidity_imbalance(uint256[3] calldata amounts, uint256 max_burn, bool use_eth, address receiver) external returns(uint256[3] memory); function remove_liquidity_one_coin(uint256 token_amount, uint256 coin_index, uint256 min_amount, bool use_eth, address receiver) external returns(uint256[3] memory); } ``` We can see the `exchange` function which has several parameters we'll need to provide. ```javascript function exchange( uint256 i, uint256 j, uint256 dx, uint256 min_dy, bool use_eth, address receiver ) external; ``` In our test, we'll call `pool.exchange` with the parameters enclosed in curly braces for clarity. ```javascript pool.exchange({ uint256 i, uint256 j, uint256 dx, uint256 min_dy, bool use_eth, address receiver }); ``` The parameter `i` is the index of the token we are sending, which is WETH, or `2`. The parameter `j` is the index of the token we are receiving, which is USDC, or `0`. `dx` is the amount of WETH we are sending, which is `1e18`, or 1 WETH. `min_dy` is the minimum amount of USDC we expect to receive, which we'll set to `1`. The parameter `use_eth` is `false` since we are using WETH, not ETH. Finally, the receiver address is the address of this contract, `address(this)`. ```javascript pool.exchange({ i: 2, j: 0, dx: 1e18, min_dy: 1, use_eth: false, receiver: address(this) }); ``` This completes the second exercise. Let's try executing the test. We'll execute the `test_exchange` function using the forge command with a match test flag: ```bash forge test \ --evm-version cancun \ --fork-url $FORK_URL \ --match-test test_exchange \ --match-path test/curve-v2/exercises/CurveV2Swap.test.sol -vvv ``` After running the test, we can see that our test passed and we received approximately 3080 USDC for swapping 1 WETH.