A grocery sells bag of 6 oranges for 4.38 what is the unit cost on the double number line below fill in the given values then use multiplication it division to find the missing Value

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.