c.
As found in part (a), the data in the table can be represented by the linear model as follows,
Here, 'x' is the number of years after year 2000.
To find: The population in 2080 as predicted by the model.
The value of 'x' corresponding to the year 2080 can be obtained as follows,
Substitute the value of 'x' in the model for population,
Thus, the population in 2080 will be 504.9 million approximately, as predicted by the linear model.