Question

For my class you have to choose from several different scenarios, make up your own equations from the scenario, and then solve and graph them in excel. I have chosen the following scenario:

Evaluate whether a prepaid or monthly cell phone plan is most effective for a customer that uses x weekday minutes per month.

I can do the math part of the problem myself, the part I am having trouble with is coming up with the equations. It is worded in the problem like this:

Develop an algebraic equation with clearly defined variables to represent the cost/yield of each option.

We are aloud to make up any numbers that we want.