Suppose the long-distance phone companies in Example A calculate their charges so that a call of exactly 3 min will cost the same as a call of 3.25 min or 3.9 min, and there is no increase in cost until you have been connected for 4 min. Increases are calculated after each additional minute. A function that models this situation is the greatest integer function, y = [x], which outputs the greatest integer less than or equal to x.
a. Use the greatest integer function to write cost equations for the two companies in Example A.
b. Graph the two new equations representing the Phrequent Phoner Plan and the Small Business Plan.
c. Now determine when each plan is more desirable. Explain your reasoning.