Problem:

A real estate agent is considering changing her cell phone plan. There are 3 plans to choose from all which have a montly service fee of $20. Plan A has a rate of $.45 cents for daytime min and $.20 for evening. Plan B $.55 day and $.15 evening. Plan C has a flat rate of $80 for 200 minutes of calls and a charge of $.40 beyond that 200 if either day or night.

Required:

Question 1) Suppose that the agent expects both daytime and evening calls. At what point (ie percentage of call minutes for daytime calls) would she be indifferent between plans A and B?

Solve the problem and show all work.