Since xrepresents the number of years since 2003:
2003 # x=0
2007 # x=4
The average rate of change from 2003 to 2007 is:
(f(4)-f(0))/(4-0)
Find f(0):
f(0)=280× # 1.08 # ^0
f(0)=280
Find f(4):
f(4)=280× # 1.08 # ^4
f(4)#380.94
Now calculate:
(380.94-280)/4
=100.94/4
#25.23
Rounded to the nearest whole number:
25
Since the value is positive, the number of subscribers is increasing.
So the correct interpretation is:
" The number of subscribers increases at an average rate of 25 subscribers per year. " Therefore, the correct answer is:
# ( " C " )