The table shows world average daily oil consumption from 1985 to 2010 measured in thousands of barrels per day.

(a) Compute and interpret the average rate of change from 1990 to 2005. What are the units?

(b) Estimate the instantaneous rate of change in 2000 by taking the average of two average rates of change. What are its units?

Years since 1985............................. Thousands of barrels of oil per day

0........................................................................... 60,083

5........................................................................... 66,533

10......................................................................... 70,099

15......................................................................... 76,784

20......................................................................... 84,077

25......................................................................... 87,302