Microeconomics and Pricing

For perfectly elastic goods, demand is extremely sensitive to price changes. Any price increase causes demand to fall to zero because consumers can easily switch to substitutes or simply stop buying. This contrasts with inelastic goods where demand remains stable despite price changes.

Transaction demand for money refers to money people hold to facilitate everyday transactions - buying goods, paying bills, meeting regular expenses. This demand is directly proportional to income - higher income means more transactions and thus higher demand for money for transaction purposes. While interest rates affect speculative demand for money (holding money vs bonds), transaction demand primarily depends on the level of income in the economy.

The investment multiplier (k) is calculated as k = 1 / (1 - MPC) or alternatively k = 1 / MPS, where MPC is marginal propensity to consume and MPS is marginal propensity to save. Given MPC = 0.75, we have MPS = 1 - 0.75 = 0.25. Therefore, k = 1 / 0.25 = 4. The multiplier shows that an initial investment of Rs. 1 will ultimately increase national income by Rs. 4 through the multiplier process of successive rounds of spending.

The Cobb-Douglas production function (Y = A·K^α·L^β) has a unitary elasticity of substitution equal to one. This means the percentage change in the capital-labor ratio divided by the percentage change in the marginal rate of technical substitution equals one. This constant unitary elasticity is a defining property that makes Cobb-Douglas analytically tractable.

Liquidity trap occurs when the liquidity preference curve becomes perfectly elastic (horizontal) at very low interest rates. People are indifferent between holding bonds and money, so monetary policy becomes ineffective. Unitary elastic, perfectly inelastic, and simply inelastic curves don't describe this situation.

The law of Equi-Marginal Utility states that a consumer maximizes satisfaction when the marginal utility per rupee spent is equal across all goods consumed. Mathematically, this means MUx/Px = MUy/Py = MUz/Pz. At this point, the consumer cannot increase total utility by reallocating expenditure.

For profit maximization, a monopolist produces where Marginal Revenue (MR) equals Marginal Cost (MC). The slope of the total cost curve gives MC = 12. Therefore, at the profit-maximizing output level, MR must equal MC, which is 12. The average cost (AC = 15) is irrelevant to this condition.

When the price of a normal good falls, consumers buy more due to two effects: (1) the substitution effect - the good becomes cheaper relative to substitutes, and (2) the income effect - the consumer's purchasing power increases. Both effects work in the same direction for normal goods, increasing quantity demanded.

For a normal commodity, the substitution effect is always negative (inverse relationship between price and quantity). When price falls, the substitution effect always leads to increased consumption of that good as it becomes relatively cheaper compared to substitutes. This is a fundamental principle in consumer theory.

The Average Revenue (AR) curve represents revenue per unit sold, which equals price under standard market conditions. Since price and quantity demanded have an inverse relationship per the Law of Demand, the AR curve maps the same relationship as the Demand Curve. For a perfectly competitive firm, AR equals marginal revenue and market price, making it coincident with the horizontal demand curve.

When demand is highly inelastic (consumers are relatively unresponsive to price changes), sellers can pass the tax burden onto buyers by increasing prices. If demand were elastic, consumers would reduce purchases significantly in response to price increases, making it difficult to add taxes to prices. This is why 'sin taxes' on addictive goods (with inelastic demand) are effective.

When total product increases at an increasing rate, the marginal product must be rising. This is because marginal product is the derivative of total product - it measures the additional output from each extra unit of input. If total product is accelerating, marginal product is positive and increasing.

Perfect competition achieves the most efficient allocation of resources because it ensures allocative efficiency (P=MC) and productive efficiency. In perfect competition, firms are price takers, there is free entry and exit, perfect information, and homogeneous products - all conditions that maximize social welfare and minimize deadweight loss.