Which situation could be modeled by using a linear function?

(1) a bank account balance that grows at a rate of 5% per year,

compounded annually

(2) a population of bacteria that doubles every 4.5 hours

(3) the cost of cell phone service that charges a base amount plus

20 cents per minute

(4) the concentration of medicine in a person’s body that decays by

a factor of one-third every hour