From 1990 to 1997, the number of cell phone subscribers S (in thousands) in the US can be modeled by, S = 5535.33(1.413)x where ‘x’ is number of years since 1990. a ) Identify the growth factor (constant ratio) and annual percent increase

b) In what year was the number of cell phone subscribers about 31 million? How do you know?

c ) According to the model, in what year will the number of cell phone subscribers exceed 90 million? How do you know?

d ) Determine the number of subscribers in 2010. How do you know?