A real estate agent is considering changing her cell phone plan. there are 3 plans to choose from, all of which involve a weekly service charge of $20. plan A has a cost of $0.45/min for daytime calls and $0.20/min for evening calls. plan B has a charge of $0.55/min for daytime calls and $0.15/min for evening calls. plan C has a flat rate of $80 with 200 minutes of calls allowed per week and a charge of $0.40 per minute beyond that, day or evening.

Determine the total charge under each plan for this case: 120 minutes of days calls and 40 minutes of evening calls in a week

Prepare a graph that shows total weekly cost for each plan versus daytime call minutes

If the agent will use the service for daytime calls, over what range of call minutes will each plan be optimal?

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