In 1970 Professor Fellswoop earned $12,000; in 1980 he earned $24,000; and in 1990 he earned $36,000. If the CPI was 40 in 1970, 60 in 1980, and 100 in 1990, then in real terms, Professor Fellswoop's salary was highest in.

In 1980

Explanation:

Year        Salary        Percentage Salary Increase        CPI Increase

1970       $12,000     -                                                      -

1980       $24,000    100                                                 50

1990       $36,000    50                                                   83.3

As can be seen in the table, the Professor's salary increase from 1970 to 1980 was twice as much as the CPI increase during the same period.

On the contrary, his salary increase from 1980 to 1990 was significantly less than the CPI increase during the same period.

Therefore, the professor's salary was highest in 1980.

answer; closing the loop;

answer/// real gdp decreases to y3 and the price level falls to p3;