A real estate agent buys mobile phone plans. There are three billing plans to choose from. Plans A and B have a basic weekly fee of $20. Plan A costs $0.45 per minute for calls made during the day and $0.20 per minute for calls made at night. Plan B charges $0.55 per minute for daytime calls and $0.15 per minute for evening calls. Plan C has a flat fee of $80 for 200 minutes of calls per week and a fee of $0.40 per excess minute, day or night.

If the agent uses this service for daytime calls only, draw a graph that plots the total weekly charges for each of the plans against daytime calling minutes.