Step 1: Concept
To find which plan that cost more, you will trace the time at from the horizontal axis to the point where its intercept the lines.
Step 2:
a) For 20 minutes of long-distance calls for a month
Plan A cost $2
Plan B cost $8
Plan B cost $6 more than plan A
Step 3:
b)
Plan A and plan B cost the same amount for a long-distance call of
140 minutes
Plan B cost less