Final answer:
The rate of change in vehicle emission standards regarding hydrocarbons released per mile between 1968 and 1980 was approximately 0.491 hydrocarbons per mile per year.
Step-by-step explanation:
The rate of change in vehicle emission standards between 1968 and 1980 can be found by calculating the difference in the allowed hydrocarbons per mile driven in those years and then dividing by the number of years between them. In 1968, the emission standard was 6.3 hydrocarbons per mile, and by 1980 it was reduced to 0.41 hydrocarbons per mile.
To find the rate of change, subtract the standard in 1980 from the standard in 1968: 6.3 - 0.41 = 5.89 hydrocarbons per mile. Then divide this difference by the number of years (1980 - 1968 = 12 years): 5.89 ÷ 12 = 0.491 hydrocarbons per mile per year.
Therefore, the rate of change of the vehicle emission standards regarding hydrocarbons released per mile from 1968 to 1980 was approximately 0.491 hydrocarbons per mile per year.