Lucian and Blake are taking their bikes out to a nature trail in the woods. They want to be out for no more than 6 hours, and they want to travel at least 40 miles between walking and biking. On average, they walk at a rate of 3 miles/hour and bike at a rate of 12 miles/hour. Which graph represents the number of hours Lucian and Blake can spend either walking or biking to meet their goals?