The market demand curve of a good that is rival in consumption and excludable is the horizontal sum of the individual demand curves. However, the marginal social surplus curve of a public good is the vertical sum of the individual marginal benefit curves. What aspect of a public good causes the demand curves to be summed vertically instead of horizontally

About 20 years ago, sturdy light, inc., produced a sturdy, lightweight backpack in a market that was rapidly growing. sturdy light became a leader in this market. eventually, the backpack market reached the maturity stage and slowed down. however, by this time, sturdy light had developed a strong brand name and continued to steadily lead the market. which of the following describes this scenario? a. sturdy light was a star that developed into a cash cow. b. sturdy light was a question mark that developed into a star. c. sturdy light was a dog that developed into a question mark. d. sturdy light was a cash cow that developed into a star.