To determine wether of not it is linear, you will need to see if it has a constant rate of change, if it does it is a linear function, if it doesn't it is non-linear. and to find the rate of change you will need to find the slope.
To find the rate of change, count the rise and run between two points. Then divide the rise by the run. If the rate of change is constant between all points, then the function is linear and it will be a straight line.
Well, its 10 for 4. so 8 is 20, 12 is 30, 16 is 40 20 is 50, and 24 is 1 hour, 2 tabels is half the time so 5 min... so it would take -1 hour and 5 min
