What was the gross weight of the package in kilograms ? if shipping costs 74 cents per kilogram how much did the package cost to send in dollars

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.