00:01
So here we have a cross elasticity.
00:03
What is a cross elasticity? so cross elasticity measures how the quantity of one good a responds to a percentage change in another good b, right? so here you have the different goods being compared.
00:19
Normally the elasticity is how the quantity responds to its own price, but across elasticity is how the quantity of one good responds to a change in the price of another good.
00:30
And we're told that this is minus five.
00:32
So it is negative.
00:34
How can we interpret this, right? well, let's suppose the price of b is going up.
00:42
We know from the cross elasticity that it means the quantity of a must be going down, right? if this is positive, this must be negative.
00:52
So if price of b is a positive percentage change.
00:55
The quantity of a has to be a negative percentage change to generate a negative cross elasticity.
01:02
So this is my cross elasticity.
01:08
But can we fill in the missing piece here? the missing piece is if price of b goes up, we should expect the quantity of b to go down.
01:17
This is what we call the law of demand, right? law of demand...