Plan A Plan B
Cost for 100 minutes (¢) 1,000 2,000 + 500 = 2,500
Cost for 200 minutes (¢) 2,000 2,000 + 1,000 = 3,000
Cost for 300 minutes (¢) 3,000 2,000 + 1,500 = 3,500
Cost for 400 minutes (¢) 4,000 2,000 + 2,000 = 4,000
You can see that, starting with the 401st minute, Plan B is the cheaper plan.
.