[Solved] One of the most serious invasion of privacy issues with respect to e-commerce is A) access to pornography sites. B) downloading copyrighted material. C) collection and use of personal information. D) sharing medical information with unauthorized users. Purely Competitive Seller: A market participant in an industry where many sellers offer identical products, and no single seller can influence the market price. MR = MC Rule: An economic principle stating that profit maximization for a firm occurs when its marginal revenue (MR) equals its marginal cost (MC). Purely Competitive Seller: A seller in a perfectly competitive market where the product offered has no differentiation, and the seller is a price taker with no control over the market price. MR = MC Output: The condition where Marginal Revenue (MR) equals Marginal Cost (MC) represents the profit-maximizing level of output for a firm.