 Ryan asks, after reading this week's coursework, I was interested in checking out the blockchain explorer on blockchain.com. I saw a mining pool named F2Pool quite often, and I noticed that on October 3rd, 2019, they mined 18 blocks. Is it fair to assume then that this pool alone potentially made a gross profit of $1.8 million in one day, not including transaction fees? What are the economics of these pools? How much of that $1.8 million is potentially profit? It depends. It depends on the electricity cost, operational cost, and hardware cost of the miners who are participating. Now, keep in mind, and this is really, really important, mining pools are not miners. Miners are the people with the hardware. Mining pools are the coordinators who help the miners collaborate so they can smooth out their earnings. It's not the mining pool that mined these things. It's actually the miners who participate in that pool who mined these blocks. And how much of that $1.8 million was profit? We don't know. The profit ranges between zero, in many cases. Some of these are not profitable. In some cases, up to 30% or more when the cost of electricity is low, the price of Bitcoin is high, the hash rate of a specific miner is high, and they're able to get lots and lots of blocks, and even more so when the transaction fees are high. So the profit margin depends on all of these factors, which are highly, highly individualized. Different miners have different profit margins and operating costs, which actually is a great way for the system to dynamically balance. Ryan asks, given the race by both users with fees and miners with hashing, is it possible that some wallets secretly working with certain pools can send transactions directly to the mem pool of those mining pools first or a few seconds before everybody else, and give them a slight edge to build an ideal block or create higher fees? Yes, this is in fact possible, not just possible, it has happened. There are times in the network where miners have created their own transactions with elevated fees, injected them into the mem pool of various mining pools that they're well connected to, where they get propagated very, very fast, causing the mem pool to have lots of high fee transactions, and then that causes all of the other users who want to put in transactions to elevate their fees. Now this is a strategy that is very risky. If a miner that is constructing these in collaboration with some wallet that they've built to do this, to jam high fee transactions into the mem pool in order to elevate the prices, if that miner isn't actually mining those transactions, effectively they're spending these fees and paying the other miner that ended up mining these transactions. So the strategy only works for miners who have a very high percentage of the hash rate, so they can recoup some of the fees they're spending trying to jam the market. Of course, if all miners are doing this and they do this kind of collusion, then what happens is that fees can be elevated. However, keep in mind from a game theory perspective, if you're one of the miners and you notice all of your colleagues are jamming transaction with high fees into the mem pool to drive up fees, what you can do is sit back, not pay a thing, and let them drive up fees while you just earn them by mining and you're not risking these transactions that might be mined by someone else, which means that you make as much money as they make per your hashing power from the higher fees, but you're not spending money to create these higher fees. Well, if you think about it, if everybody does that, then nobody is willing to take the risk of creating the high fee transactions because those would benefit all of the other miners and they'd be taking on all of the costs. It's a classic tragedy of the common scenario and in this particular case it works the benefit of users because this only works if there's a lot of collusion between a lot of miners who have a lot of hash power during a time when fees are already high and there's some kind of political fight going on, which is why this happened mostly in the summer preceding the hard fork of Bitcoin cash and the huge debate over scaling where people wanted to make a point about how full the system was. Now, it may happen from time to time again, but it's a risky strategy for miners that they can only pull off when there's a lot of collusion and where miners can easily reap all the benefits and pay none of the costs by taking advantage of that, so it's a losing strategy most of the time.