3.1) A natural monopoly arises when a single firm can supply an entire market at a lower cost than two or more firms due to significant economies of scale and high fixed costs, such as in utility industries. An artificial monopoly is created by barriers to entry that are not inherent to the industry's cost structure, such as patents, licenses, control over essential resources, or government regulations. 3.2) A monopoly faces a downward-sloping demand curve because it is the sole supplier in the market, meaning the firm's demand curve is the market demand curve. To sell more units, the monopolist must lower its price. This gives the monopolist control over price, making it a price maker rather than a price taker. However, this control is not absolute; the monopolist can choose either the price or the quantity to sell, but not both independently, as it is constrained by the market demand curve. 3.3) Monopolies can have several effects on the economy. They often lead to higher prices and lower output compared to competitive markets, resulting in allocative inefficiency (P > MC) and a deadweight loss to society. They may also exhibit productive inefficiency by not producing at the lowest possible average cost. However, monopolies can sometimes achieve significant economies of scale, especially natural monopolies, which can lead to lower costs for consumers than if multiple smaller firms operated. Furthermore, the prospect of supernormal profits can incentivize innovation and research and development. 3.4) Inefficiency in a monopoly occurs in several ways. Firstly, there is allocative inefficiency because the monopolist sets price above marginal cost (P > MC), meaning that society values additional units of the good more than the cost to produce them, but these units are not produced. Secondly, productive inefficiency can occur as the monopolist does not necessarily produce at the minimum point of its average total cost curve. Lastly, a lack of competition can lead to X-inefficiency, where the firm's costs are higher than necessary due to complacency and a lack of pressure to minimize expenses. That's 2 down. 3 left today — send the next one.