- [Instructor] We've spent several videos
talking about the costs of a firm.
And in particular, we've thought about
how marginal cost is driven by quantity
and how average total cost
is driven by quantity,
and we think about other
average costs as well.
Now, in this video, we're
going to extend that analysis
by starting to think about profit.
Now, profit, you are probably
already familiar with the term.
But one way to think
about it, very generally,
it's how much a firm brings in,
you could consider that its revenue,
minus its costs,
minus its costs.
And a rational firm will
want to maximize its profit.
And so to understand how a firm
might go about maximizing its profit
or what quantity it would need to produce
to maximize its profit based on this,
on its cost structure,
we have to introduce revenue
into this model here.
And in particular, we are going
to introduce the idea of marginal revenue.
And we're going to assume
that this firm is in a
very competitive market,
and so it is a price-taker.
So regardless of how
much this firm produces,
the incremental revenue per
unit of what it produces,
maybe this is a doughnut company,
the incremental amount per doughnut
is going to stay the same regardless of
how much this firm in particular produces.
So let's say that the marginal
revenue in this industry,
in this market, is right over here.
So one way to think about it is
this would be the unit
price in that market.
So let me put that right
over there, marginal revenue.
Once again, for every incremental unit,
how much revenue you're going to get,
so it would just be
the price of that unit.
So how much would a rational firm produce
in order to maximize its profit?
If the marginal revenue is
higher than the marginal cost,
well, that means every
incremental unit it produces,
it's going to bring in some
net money into the door.
So it's rational for it to do it.
So it would keep
producing, keep producing,
keep producing, keep producing.
Now, it gets interesting
as the marginal cost starts
to approach the marginal revenue.
As long as the marginal revenue is higher
than the marginal cost,
it's rational for the firm to produce.
But right at that unit
where the marginal cost is
equal to the marginal revenue,
well, there, on that incremental unit,
the firm just breaks even
at least on the margin.
It might be able to utilize
some of its fixed costs a little bit.
But then, after that point,
it makes no sense at all
for it to keep producing.
Why is that?
Well, if the marginal cost is higher
than the marginal revenue,
that would be like saying,
hey, I'm gonna sell a doughnut for $1
even though that incremental doughnut
costs me $1.10 to produce.
Well, no rational person,
if they want to maximize
their profit, would do that.
So a rational firm that's trying
to maximize its profit
will produce the quantity
where marginal cost
intersects marginal revenue.
It will produce this quantity
right over there.
Now, a natural question might be
how much profit will it make
from producing that quantity?
Well, all you have to do is think about,
this is the marginal revenue that it gets,
and another way you could think about it,
because this is constant,
it's also going to be
the average revenue that it gets per unit.
And this right over here,
is the average total cost per unit.
And so what you could do is,
this is how much it's
getting on average per unit,
and then multiply that
times the number of units.
And what you get is the
area of this rectangle.
So for those of you who
are more visually inclined,
one way to think about it
is a profit-maximizing firm,
a rational profit-maximizing firm,
would want to maximize this area.
Think about what would happen
if they only produced this much.
Well, then they're
giving up a ton of area.
Then the rectangle would only be this big.
This would be the profit
that the firm is going to
be making from those units.
And then if it decides,
for some irrational reason,
to produce more than this quantity
that we settled on before,
let's say this right over here,
notice even though that the base
of this rectangle is
longer, the height is less,
and this would actually have a lower area.
And the reason why I feel
very confident that this
will have a lower area is
because, in this situation,
the firm is losing money on
all of these incremental units
where the marginal cost is
higher than the marginal revenue.
So big takeaway, a rational firm
that's trying to maximize its profit
will produce the quantity
where marginal cost
and marginal revenue
are equal to each other.
