Grade 11 Economics: Chapter 2 Lesson 2.2.2

In economics, what defines the short run?

A period of time in which the quantity of at least one input is fixed, while the quantities of other inputs can be changed.

In economics, what defines the long run?

A period of time in which the quantities of all inputs can be varied.

Is there a fixed calendar time (like 6 months or a year) that separates the short run from the long run?

No. There is no fixed calendar time; the distinction between short run and long run varies from one industry to another.

What are the two primary approaches used to explain or calculate a competitive firm's short-run equilibrium?

1. The Total Revenue ($TR$) – Total Cost ($TC$) approach 2. The Marginal Revenue ($MR$) – Marginal Cost ($MC$) approach

What is the fundamental goal of combining revenue and cost functions in both equilibrium approaches?

To determine the exact amount of goods and services a firm must produce at the given market price to maximize profit or minimize losses.

Under the Total Revenue – Total Cost Approach, how behaves the slope of the $TR$ curve for a perfectly competitive firm?

It is a straight line sloping upward, where the slope is exactly equal to the price of the good.

Under the Total Revenue – Total Cost Approach, at what specific output quantity does a firm achieve maximum profit?

At the quantity where the vertical gap of total revenue over total cost is the largest.

Why does the Marginal Revenue ($MR$) of a perfectly competitive firm remain constant and flat as it produces more output?

Because the firm is a price taker; the additional revenue gained from selling one more unit is always exactly equal to the constant market price.

Describe the general behavior of the Marginal Cost ($MC$) curve in the short run as output increases.

It is initially downward-sloping (due to increasing marginal returns at low output levels) but eventually slopes upward at higher levels of output due to diminishing marginal returns.

What is the first (necessary) condition for a firm's equilibrium using the Marginal Revenue – Marginal Cost Approach?

Marginal Revenue must equal Marginal Cost ($MR = MC$). (For a competitive firm, this can also be written as $P = MC$ ).

Why is the condition $MR = MC$ necessary but not sufficient on its own for equilibrium?

Because the curves can cross at multiple points; a second condition is required to ensure the firm is truly maximizing profit rather than minimizing it.

What is the second (sufficient) condition for short-run equilibrium under the $MR=MC$ approach?

The $MC$ curve must be rising at the point where it intersects the $MR$ curve (meaning $MC$ must cut the $MR$ line from below).

Under what cost condition will a perfectly competitive firm earn a positive economic profit?

When the market price is greater than the average total cost ($P > AC$) at the profit-maximizing quantity.

What happens to a firm's profits when the market price is exactly equal to the average cost ($P = AC$)?

The firm earns zero economic profits (also known as the break-even or zero-profit point), which occurs at the minimum point of the $AC$ curve.

If a firm is making losses in the short run, why doesn't it immediately avoid losses by dropping production to zero?

Because the firm must still pay its fixed costs in the short run even if it produces nothing. Shutting down only reduces variable costs to zero.

What is the shutdown rule for a short-run firm experiencing losses?

Continue operating: If the price is between the shutdown point and break-even point, because it covers all variable costs and some fixed costs.

Shut down immediately: If the price falls below the shutdown point ($P < AVC$), because it fails to even cover its variable costs.

What exact economic intersection defines a firm's shutdown point?

The intersection of the Average Variable Cost ($AVC$) curve and the Marginal Cost ($MC$) curve.