A truck gets 10 miles per gallon of diesel fuel traveling along an interstate highway at 50mph. This mileage decreases by 0.15mpg for each mile per hour increased above 50mph. The truck driver is paid $30 per hour, and diesel fuel costs P = $3.00 per gallon.
Suppose that the price for diesel fuel goes down to P=$2.00 per gallon. Do you expect the optimal speed v to increase or decrease? Why would this be so?