The town of Happyville recorded the following census figures: In 1970, the population was 20,000 and
because of a new business coming to town, the
population rose to 25,000 in 1980. Over the next ten
years, the population rose to 28,000 in 1990. In 2005,
the business declared bankruptcy and the population
dropped to 20,000. What is the average rate of change
the population of Happyville over the time interval
from 1970 to 2005?