A phone company charges its customers as follows:
For the first 500 minutes used each month, the customer is charged a flat rate of $50. These 500 minutes are "included" in their monthly plan.
For any additional minutes used, the customer is charged an additional $.10 per minute.
Which type of function would best model this situation: a greatest integer function or a piecewise function that is not a greatest integer function? Explain.

Question

A phone company charges its customers as follows: 
For the first 500 minutes used each month, the customer is charged a flat rate of $50.  These 500 minutes are "included" in their monthly plan.
For any additional minutes used, the customer is charged an additional $.10 per minute.
Which type of function would best model this situation: a greatest integer function or a piecewise function that is not a greatest integer function?  Explain.