The expression 12g gives the number of kilometers a car can travel using g liters of gasoline. how far can this car travel on 5 1/2 liters of gasoline?

In order for the function to be linear, what must m be and why? m = 22 because the rate of change is 1. m = 20 because the rate of change is 3. m = 22 because the rate of change is -1. m = 20 because the rate of change is -3.