Posted: September 12th, 2015

Kim Davis has decided to purchase a cellular phone, but she is unsure about which rate plan to select.

Kim Davis has decided to purchase a cellular phone, but she is unsure about which rate plan to select. The regular plan charges a fixed fee of $55 per month for 1,000 minutes of airtime plus airtime plus $0.33 per minute for any time over 1,000 minutes. The executive plan charges a fixed fee of $100 per month for 1,200 minutes airtime plus 200 minutes airtime plus $0.25 per minute over 1,200 minutes.

a. If Kim expects to use the phone for 21 hours per month, which plan should she select?

b. At what level of use would Kim be indifferent between the two plans?