00:01
Number 58 says that there's a basic phone plan with the basic charge of $35 a month, which includes 400 free minutes and charges 10 cents for each additional minute of usage.
00:12
So the first thing we can do is, and they want us to write the monthly cost of the function of x and to graph it.
00:22
So the first thing you can do is graph it.
00:25
So we have x, which is minutes, and we have.
00:33
Have y, which is cost.
00:39
So 100, 200, 300, 400, 600, 600, 600, 600, and so as they want us to go from zero to 600 inclusive.
00:50
Here's 400.
00:52
And on this side, we'll just put 10, 20, 30, 40, and so on.
01:09
So the first thing we're going to graph is that from zero to 400 minutes, it's $35.
01:16
So 35 is about here, and 400 is about here.
01:21
So from 35 to 400, it's a straight line.
01:26
And then after that, they charge 10 cents for each additional minute.
01:30
So how we can figure that out what this part of the function will be.
01:40
Is we can say, suppose you talk for 50 extra minutes...