Answer to Question #49177 in Linear Algebra for gigi

Question

Wizard Mobile offers customers a choice of several monthly plans. The two least expensive ones are
Plan A and Plan B. Plan A, Pay As You Go, has no fixed monthly charges, and each minute costs 40
cents. Plan B charges $30 a month, includes 100 free minutes, and each additional minute costs 50
cents.
(a) For plan A: write a formula describing the monthly costs as a function of x, the number of
minutes the phone is used. Graph your equation, carefully labeling the axes. What is the interpretation of the y-intercept and the slope of this function?
(b) For plan B: write a formula describing the monthly costs as a function of x, the number of
minutes the phone is used. Graph the function on the same axes as the first function, carefully
labeling the axes. What is the interpretation of the y-intercept of this function?
(c) Give an example of the number of minutes used in a month (bigger than 0) for which plan A is
cheaper than plan B.
(d) Give an example of the number of minutes for which plan B is cheaper than plan A.
(e) Do the graphs of the two functions intersect? If so, what is the interpretation of the point(s) of
intersection? Explain.