18- Marginal cost-Marginal revenue formula should be considered for; a-Optimizing unit with profit maximization. b- For determining the minimum cost amount. c- Demand and supply equilibrium. d-For preventing supply surplus. 19- Opportunity cost IS: a- What we gain from all alternatives. b- The cost of all available choices. The cost of (chosen alternative-the cost of unchosen alternatives). - The cost of unknown opportunities. 20-The production factors are; Technology, factory,entrepreneurship , teamwork b- Land, labor, raw material, output,fixed Input c. Technology, labor capital, raw material,entrepreneurship. - Land, technology , Input, factory,variable input.

18- Marginal cost-Marginal revenue formula should be considered for:<br />a- Optimizing unit with profit maximization.<br /><br />Explanation: The marginal cost-marginal revenue formula is used to determine the optimal level of production where profit is maximized. It involves comparing the additional cost of producing one more unit (marginal cost) with the additional revenue generated from selling that unit (marginal revenue). When marginal cost equals marginal revenue, profit is maximized.<br /><br />19- Opportunity cost IS:<br />c- The cost of (chosen alternative-the cost of unchosen alternatives).<br /><br />Explanation: Opportunity cost refers to the value of the next best alternative that is forgone when a decision is made. It is the difference between the cost of the chosen alternative and the cost of the unchosen alternatives. It represents the benefits that could have been gained by choosing the next best option.<br /><br />20- The production factors are:<br />c- Technology, labor, capital, raw material, entrepreneurship.<br /><br />Explanation: Production factors, also known as factors of production, are the resources used in the production of goods and services. These include technology (the application of scientific knowledge to practical purposes), labor (human effort), capital (machinery, buildings, and infrastructure), raw materials (natural resources), and entrepreneurship (the ability to combine the other factors to create value).