This table shows the value of a computer as a function of time elapsed since the computer was manufactured. Time (t, in years)
1 - $400,00 (Value/v)
3 - $100.00
5 - $25.00

The value of the computer decreased exponentially throughout the five-year period. What was the average annual amount decrease (in dollars per year) over the two-year interval from t = 2 to t = 4

(NOTE: give the answer as a positive value.)