9. 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 $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 of 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?

10. Annie Russell, a student at Tech, plans to open a hot dog stand inside Tech's football

stadium during home games. There are seven home games scheduled for the

upcoming season. She must pay the Tech athletic department a vendor's fee of $3,000

for the season. Her stand and other equipment will cost her $4,500 for the season.

She estimates that each hot dog she sells will cost her $0.35. She has talked to friends

at other universities who sell hot dogs at games. Based on their information and the

athletic department's forecast that each game will sell out, she anticipates that she will

sell approximately 2,000 hot dogs during each game. What price should she charge

for a hot dog in order to break even?

11. Hannah Byers and Kathleen Taylor are considering the possibility of teaching

swimming to kids during the summer. A local swim club opens its pool at noon each

day, so it is available to rent during the morning. The cost of renting the pool during

the10-week period for which Hannah and Kathleen would need it is $1,700. The pool

would also charge Hannah and Kathleen an admission, towel service, and life guarding

fee of $7 per pupil, and Hannah and Kathleen estimate an additional $5 cost per

student to hire several assistants. Hannah and Kathleen plan to charge $75 per

student for the 10-week swimming class.

a. How many pupils do Hannah and Kathleen need to enroll in their class to break

even?

b. If Hannah and Kathleen want to make a profit of $5,000 for the summer, how

many pupils do they need to enroll?

c. Hannah and Kathleen estimate that they might not be able to enroll more than

60 pupils. If they enroll this many pupils, how much would they need to charge

per pupil in order to realize their profit goal of $5,000?