Mary can choose Plan A or Plan B for her long distance charges. For each plan, cost (in dollars) depends on minutes used (per month) as shown below.(a) If Mary makes a 150 minutes of long distance calls for the month, which plan costs less? Plan A / Plan B(B) For what number of long distance minutes do the two plans cost the same If the time spent on long distance calls is less than this amount, which plan costs less? Plan A / Plan B

(A) Observe carefully, that the time in minutes for every call is recorded on the horizontal axis, or the x-axis. When the value of the x-axis is 150 (minutes), then the blue line is 12 (plan A), while the red line is 14(plan B).

This means, when she makes a 150-minute call, plan A costs $12 while plan B costs $14. Therefore, the answer to part (A) is Plan A.

(B) The two plans cost the same at the point where both the blue line and the red line intersect. Observe carefully on the graph and you'll discover that point is 200 on the x-axis. Hence, the answer to part (B) is 200 minutes.

(C) The amount spent on long distance calls at this point is $16. However if the time spent on long distance calls is less than 200 minutes, then plan A costs less. Observe closely that as you move to a point less than 200 minutes on the x-axis (move backwards or to the left side), then the two lines no longer intersect, but one of them would be slightly beneath the other, and that is plan A (the blue line). This means if the time spent on long distance calls is less than this amount, then plan A costs less.