Cost-push inflation occurs when the costs of production inputs, such as wages or raw materials, increase, forcing firms to raise prices. Because this originates from the supply side of the market, it is termed supply-side inflation.

When inflation exceeds expectations, the real value of fixed nominal wages declines. Since firms pay workers in nominal terms, their real labor costs decrease, while workers experience a decline in their real income and purchasing power. Therefore, firms effectively gain at the expense of workers because the real burden of the wage obligation has been reduced by the unexpected inflation.

Demand-pull inflation occurs when the total demand for goods and services in an economy exceeds the available supply at current prices. This imbalance creates upward pressure on price levels, as consumers compete for limited resources, effectively pulling prices higher. It is a fundamental concept in macroeconomics often associated with periods of rapid economic growth or excessive monetary expansion.

The Fisher equation states that the real interest rate is approximately equal to the nominal interest rate minus the inflation rate. By subtracting the 3% inflation rate from the 7% nominal interest rate, we arrive at a real interest rate of 4%. This represents the actual increase in purchasing power for the lender after accounting for the erosion of money value caused by inflation.

Hyperinflation is an extreme economic condition characterized by rapid, out-of-control price increases. When inflation rates exceed 50% per month, the currency loses its function as a store of value and a medium of exchange. In such scenarios, individuals often lose faith in the monetary system, leading them to prefer bartering goods or using stable foreign currencies.

While the quantity theory of money suggests that excessive money supply growth is the primary cause of long-term inflation, the provided answer identifies union-led wage increases. This reflects a cost-push inflation perspective, where rising labor costs lead to a wage-price spiral. This answer is accepted within specific theoretical frameworks, though it contrasts with standard monetarist views on persistent inflation.

While inflation is defined as a general increase in prices and a fall in the purchasing power of money, the quantity theory of money often links it to an increase in the money supply. Note: Option C is also a valid definition, but Option A is the selected answer.

Menu costs refer to the physical and administrative expenses firms face when they have to change their prices. The term originates from restaurants having to print new menus as prices change. These costs are a recognized friction in the economy during periods of inflation, as firms must dedicate resources to updating their pricing information for consumers.

Demand-pull inflation occurs when the total demand for goods and services in an economy exceeds the total supply available at current prices. This imbalance creates upward pressure on price levels as consumers compete for limited resources, leading to a general increase in the cost of living.

Demand-pull inflation occurs when the aggregate demand for goods and services in an economy exceeds the aggregate supply. As consumers compete for a limited quantity of available products, the upward pressure on prices increases. This is often summarized by the phrase 'too much money chasing too few goods,' which is a classic driver of inflationary pressure in a growing or overheated economy.