Average speed: A commuter regularly drives 70 miles from home to work, and the amount of time required for the trip varies widely as a result of road and traffic conditions. The average speed for such...

Average speed: A commuter regularly drives 70 miles from home to work, and the amount of time required for the trip varies widely as a result of road and traffic conditions. The average speed for such a trip is a function of the time required. For example, if the trip takes 2 hours, then the average speed is 70 2 = 35 miles per hour.

a. What is the average speed if the trip takes an hour and a half?

b. Find a formula for the average speed as a function of the time required for the trip. (You need to choose variable and function names. Be sure to state the units.)

c. Make a graph of the average speed as a function of the time required. Include trips from 1 hour to 3 hours in length.

d. Is the graph concave up or concave down? Explain in practical terms what this means.