7.3, production, the cost curve for Beautiful
Cars. Beautiful Cars is an imaginary company

that produces luxury cars and the strategy
of this company is to produce a small number

of cars but try to make a large profit on
each car produced. So let's get inside this

factory. This is the assembly line for Beautiful
Cars. This company incurs two types of costs:

the first type is the fixed costs, and as
the name suggests, these costs are independent

of the number of cars produced - an example
of fixed costs are the costs of research and

development that go into designing new cars,
or the advertisement cost of promoting a new

car, or the cost of patenting a new technology
that this firm is using to produce cars; the

second type of cost is the variable costs,
and as the name suggests these costs vary

or increase as we produce more and more cars.
A good example of it is the car components:

as you produce more cars, you are going to
spend more on car components, therefore your

variable costs go up. The combination of fixed
costs and variable costs give you the total

cost. Now let's go back to our textbook and
scroll down to see the concepts we talked

about depicted in a graph. Here the x-axis
represents the number of cars produced per

day, and the y-axis represents the costs.
The purple line depicts the total cost of

production and as you can see if our company
does not produce any car, it still has to

pay a fixed amount of costs which is represented
by F here. Now we introduce a new concept

which is the average cost of production, which
is the total cost of production divided by

the number of cars produced. For instance,
if our company decides to produce 20 cars,

the total cost, which is $80000 divided by
20 will get $4000, the average cost of producing

a car. If our company decides to increase
its production further from 20 to 40 cars

per day, then the average cost declines from
$4000 to $3400. But if we decide to increase

our production further from 40 to 60, our
average cost starts to increase from $3400

to $3600. So if we depict our average cost
curve, the blue curve here, we see a U shape.

At the beginning the average cost starts to
decline, why? Because at low levels of production

the fixed costs dominate the total costs.
But at some stage we start to reach the full

capacity of our given factory, and in order
to keep up with production we will have to

put more pressure on our production line,
and as a result we will have more errors and

breakdowns and the average cost increases.
So this was average cost, and it is a very

useful concept in business. The managers of
Beautiful Cars constantly think about what

price they will charge for Beautiful Cars,
and how much these cars cost to produce on

average. So let me scroll down and introduce
another concept, and that is called the marginal

cost. Marginal cost is the cost of producing
one more car. Now you might ask who in reality

thinks about this concept. Does Beautiful
Car think about the cost of producing one

more car? Perhaps not, but when they are making
a decision about whether to expand the business

or not, Beautiful Cars think about the cost
of this expansion, how much this expansion

adds to their costs. So in reality businesses
use this concept at the back of their minds.

Now let's go back to our assembly line. We
can think of the marginal cost in this way.

How much would the production of the first
car add to our total costs? How much would

the production of the second car add to our
total costs? And we can do this all the way

until the final unit which is the 20th car.
Now remember, all these cars are identical

and cost the same to produce. When we talk
about marginal cost we are simply talking

about the cost of expansion of our production,
we are not talking about the cost of a particular

car. Now we know from out textbook that the
marginal cost of producing the 20th car is

$2200. Producing the 20th car would add $2200
to our costs, and if we look at our final

costs, the marginal cost represents the slope
of this curve, how much producing the 20th

car would add to our total costs. And as you
can see, the slope of our total cost increases

as we expand production, and that means our
marginal cost is upward sloping. Now the upward-sloping

marginal cost curve means that as we move
along in our assembly line from the first

car produced to the last car produced, the
cost of producing an additional car goes up

and up. And that's because of diminishing
returns to factors of production, more specifically

here, diminishing returns to labour. To understand
diminishing returns let's think about this

example. When our factory starts, it has a
fixed set of machinery. To produce the first

batch of cars our company needs to hire three
workers. Now these workers are very productive

because they have a lot of machinery to work
with. But to further expand its production,

our company needs to hire the second group
of workers. Now these two groups of workers

need to share the same amount of machinery
with each other, therefore productivity goes

down. Again, to further expand you need to
hire more workers, now these three groups

of workers need to share the fixed machinery.
Now you get the idea: if you have a fixed

set of machinery and you keep adding labour
to your factory, the average productivity

of labour is going to go down. Therefore the
cost of expanding your production goes up

and up - the marginal cost goes up and up.
Finally, let me draw your attention to one

thing in the graph here. Here the marginal
cost curve intersects the average cost curve

at a point where average cost is the minimum.
And this has to be true by definition, why?

Because remember this is average, and this
is what we are adding to average. Let me focus

on an example. The average cost of 20 cars
is $4000. What happens if we add $2200 to

$4000? It's going to drag our average further
down. So, as long as the marginal cost curve

is below the average cost curve, is going
to drag the average down, where both these

things are the same. Here the thing we are
adding to the average is the same as average.

What is going to happen? Nothing. Here what
we are adding to average is above average,

so it's going to drag average up.