Your mother has two major routes to take to work. One alternative is to take several roads to work, and the other alternative is to use the highway. Her goal is to minimize her travel time. Over the past two months, your mother has tried each route several times under different traffic conditions. This information is summarized in minutes of travel time to work in the following table:

No Traffic Mild Traffic Severe Traffic Congestion Congestion Congestion (Minutes) (Minutes) (Minutes) Several roads 15 30 45 Highway 25 25 35