Two routes connect a suburban area and a city, with route travel times (in minutes) given by the expressions tl = 6 + 8(x1/c1) and t2 = 10 + 3(x2/c2), where the x's are expressed in thousands of vehic

Two routes connect a suburban area and a city, with route travel times (in minutes) given by the expressions tl = 6 + 8(x1/c1) and t2 = 10 + 3(x2/c2), where the x's are expressed in thousands of vehicles per hour and the c's are the route capacities in thousands of vehicles per hour.