Average revenue can be represented in a table or as a curve. For a perfectly competitive firm, the average revenue curve is a horizontal, or perfectly elastic, line. For a monopoly, oligopoly, or monopolistically competitive firm, the average revenue curve is negatively sloped.
Carbon is the main constituent of all living cells. It has chemical properties that make it the most important biological element. For instance, it forms strong chemical bonds and can form single bonds with up to four other atoms. It can bond to itself. It can also form double and triple bonds. Carbon is one of the only elements, because of its bonding properties, that can create long chain-shaped molecules or ring shaped molecules.
It is nonmetallic and tetravalent âmaking four electrons available to form covalent chemical bonds. There are three naturally occurring isotopes, with 12C and 13C being stable, while 14C is radioactive, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity.Carbon is the 15th most abundant element in the Earth's crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen.It is present in all forms of carbon-based life, and in the human body carbon is the second most abundant element by mass (about 18.5%) after oxygen.n combination with oxygen in carbon dioxide, carbon is found in the Earth's atmosphere (approximately 810 gigatonnes of carbon) and dissolved in all water bodies (approximately 36,000 gigatonnes of carbon). Around 1,900 gigatonnes of carbon are present in the biosphere.