Have vehicles gotten more fuel-efficient over the years? between 1960 and 1999 the size and shape of automobiles in the united states has changed almost annually. the amount of fuel consumed by these vehicles has also changed. the following table describes the average fuel consumption per year per passenger car in gallons of gasoline.

year, t 1960 1970 1980 1990 1995 1997 1998 1999
gallons consumed per passenger car
668
760
576
520
530
538
544
552

determine the average rate of change, in gallons of fuel used per passenger car, from 1960 to 1970.