### Exercise 3 Solution Let's go over the solutions for how to call `exactOutputSingle` on the swap router v2 contract. First, we'll type ```javascript router.exactOutputSingle ``` and then we'll check back in the interface to see what parameter we need to prepare to call the function `exactOutputSingle`. Okay, here is the function `exactOutputSingle`, and we need to prepare this parameter. We'll copy and paste that parameter. ```javascript ISwapRouter.exactOutputSingleParams({ tokenIn: tokenOut: fee: recipient: amountOut: amountInMaximum: sqrtPriceLimitX96: }) ``` We'll need to import this struct called `exactOutputSingleParams`. This is from `ISwapRouter.exactOutputSingleParams`. Token in will be DAI, token out will be WETH, and fee will be 3000. Or we can use the constant that is defined in this contract: ```javascript POOL_FEE ``` Recipient will be this contract: ```javascript address(this) ``` Amount out, in this exercise, we want to get out 0.1 WETH. WETH has 18 decimals, so 0.1 WETH will be 0.1 * 1e18. ```javascript 0.1 * 1e18 ``` Amount in maximum, we are willing to spend up to 1000 DAI, so that is ```javascript 1000 * 1e18 ``` and square root price limit X96 will be set to zero. Okay, let's try executing the test. Set the fork URL as an environment variable. Then execute the test: ```bash forge test --fork-url $FORK_URL --match-path test/uniswap-v3/exercises/UniswapV3Swap.test.sol -vvv ``` Okay, and our test passed. To get 0.1 WETH, we had to spend about 300 DAI.