A real estate agent is considering changing her cell phone plan. There are three plans to choose from, all of which involve a monthly service charge of $20. Plan A has a cost of $.38 a minute for daytime calls and $.17 a minute for evening calls. Plan B has a charge of $.47 a minute for daytime calls and $.14 a minute for evening calls. Plan C has a flat rate of $75 with 275 minutes of calls allowed per month and a charge of $.36 per minute beyond that, day or evening.