You plan on driving to a city in another state. The distance is 865 miles, your vehicle averages 18 miles per gallon of fuel, fuel costs $3.07 per gallon. You will be traveling on different highways and roads so the speed limits will vary. When considering the time that it will take you to make the journey, which of the following is a constant in the problem? O a Fuel costs $3.07 per gallon Ob The speed at which you will be traveling C The amount of rest that you will take along the trip Od The time that it takes you to make the journey