Suppose that in one week, your company takes in $2,220 in sales at one of its cell phone stores.

 Suppose that in one week, your company takes in $2,220 in sales at one of its cell phone stores. The price breakdown per phone is as follows:
Cell phone model A4: $35
Smartphone Z20: $50 
Suppose that a total of 51 phones were sold. 
Set up the system of equations that needs to be solved to determine how many of each type of phone were sold. Give a clear definition of the variables in the system.
Solve the system of equations, showing clearly how the solution was determined, and state the results clearly in light of the real-world situation.
Verify your results of the 2 linear equations by graphing in the desired graphing program and paste the graph in your assignment document (edit/copy image).
Explain how the results are verified by the graph.