The two variables that we should use are:
- x = number of minutes that the call lasted.
- y = cost of that call.
What variables should we use?
Here we want to study a relation between the cost per call as the function of the minutes that the call lasted.
So, we need to use two variables, x will be the number of minutes that call lasted, this is the independent variable.
And the variable that depends on that should be the cost of the call, let's say, y is the cost of the call.
These are the two variables that we need to model the situation:
y = f(x)
There says:
"The cost of the call is a function of the number of minutes that the call lasted".
If you want to learn more about functions, you can read:
https://brainly.com/question/4025726