00:01
Okay, guys, so this is chapter 22, problem 8.
00:05
In this question, we're given this table that is the value of watching a movie to each of these five roommates.
00:21
And it's saying buying a dvd then costs $15, but it's split evenly, so it's $3 per movie.
00:28
And this first part's asking us which number of movies maximize.
00:33
Is total surplus.
00:36
And again, our surplus is just the benefit one gets out of an item minus the cost of that item.
00:44
So for the first film, we see that quentin values at a $14 that only cost in three.
00:51
So he gets 11.
00:53
Similarly, spike.
00:54
It's worth seven.
00:56
We're at least surplus of five, surplus of one, and a surplus of minus one.
01:01
And that equals 23.
01:04
And so basically we're going to maximize surplus when the marginal surplus is zero.
01:10
So continuing down, second is worth the surplus is going to be nine for quentin.
01:17
It's going to be five for spike.
01:19
It's one for martin.
01:21
It's minus one.
01:22
Sorry, one for ridley, minus one for martin and minus three for stephen.
01:27
And that is still a total surplus for the second of 11.
01:30
The third is 7 plus 3 minus 1, minus 3, minus 3, still results in surplus of 3.
01:42
And so then for the fourth, we have 3 minus 1, minus 3, minus 3, which we now see is minus 7, which is negative, and so surplus is going to be maximized at the third movie, which means that is the efficient number of movies to watch...