Okay, here's the written lesson based on the provided video: ### Exercise 1 Solution: Uniswap V3 - Get Twap Amount Out Solution In this lesson, we'll walk through the solution to the Uniswap V3 `getTwapAmountOut` exercise. The first task is to ensure that `tokenIn` is equal to either `token0` or `token1`. We can accomplish this by using a require statement: ```javascript require(tokenIn == token0 || tokenIn == token1, "invalid token"); ``` The next task is to assign the `tokenOut` address. ```javascript address tokenOut; ``` We know that `tokenIn` is equal to either `token0` or `token1` from the previous task. Using a ternary operator we can assign `tokenOut`. If `tokenIn` is equal to `token0`, then `tokenOut` should be `token1`, otherwise, it should be `token0`: ```javascript tokenOut = tokenIn == token0 ? token1 : token0; ``` Task three is to fill out `timeDeltas` with `dt` and `0`. ```javascript uint32[] memory timeDeltas = new uint32[](2); timeDeltas[0] = dt; timeDeltas[1] = 0; ``` Next, we need to call `pool.observe`, passing in `timeDeltas`. The function returns two dynamic arrays, but we only care about the first one, which contains the tick cumulatives. ```javascript (int56[] memory tickCumulatives,) = pool.observe(timeDeltas); ``` Now we can calculate `tickCumulativeDelta`. We’ll take the difference of the tick cumulative at the first index and the tick cumulative at the zeroth index. ```javascript int56 tickCumulativeDelta; tickCumulativeDelta = tickCumulatives[1] - tickCumulatives[0]; ``` Next, calculate the average tick. Note that we must cast `dt` to a `uint56` before we can cast it to an `int56`. ```javascript int24 tick; tick = int24(tickCumulativeDelta / int56(uint56(dt))); ``` The final task is to call the `getQuoteAtTick` function. ```javascript return getQuoteAtTick(tick, amountIn, tokenIn, tokenOut); ``` Now we'll compile the contract by typing the following command in our terminal: ```bash forge build ``` We ran into a typo. Let's fix this line: ```javascript return getQuoteAtTick(tick, amountIn, tokenIn, tokenOut); ``` Let's compile again: ```bash forge build ``` Now the contract has been successfully compiled. Now, let's execute the test by first setting the fork URL environment variable. ```bash forge test --fork-url $FORK_URL --match-path test/uniswap-v3/exercises/UniswapV3Twap.test.sol -vvv ``` The test passed. The test contract instantiates the Twap contract and then calls the `getTwapAmountOut` function, passing in one WETH, a `dt` of 3600 seconds, and logs the amount of USDC that is returned. The time-weighted average price of WETH over the period of one hour is roughly 3,000 USDC.