The force of the air's resistance to a certain car (in newtons) as a function of the car's speed ((left parenthesisin \text{km/h})km/h)start text, k, m, slash, h, end text, right parenthesis is graphed. what is the approximate average rate at which the air's resistance increases, as the car accelerates from 50\text{ km/h}50 km/h50, start text, space, k, m, slash, h, end text to 65\text{ km/h}65 km/h65, start text, space, k, m, slash, h, end text?

the answer is 11 2/3 nperkm/h : )