Robin Clark Has a Cell Phone That She Uses Only

Short Answer

Robin Clark has a cell phone that she uses only for emergencies. The cost of the phone is $40 a month. The cellular company is offering unlimited nights and weekends for an additional $10 a month ($120 a year). Robin thinks it would be "cool" to have this benefit and after all $10 a month is not so much. Show Robin how much she will have in 20 years if she invests this $120 a year at 9% instead of accepting the unlimited nights and weekends offer.