 assumptions before we even proceed just like in kinetic theory of gases we have got list of assumptions, assumptions. Assumption number one inside the metal they encounter a collision. Between two collisions, it's really not influencing the motion of a force. Clear? It can affect, there can be the charges. So it may influence. Increasing temperature. So resistance just before what happens. That is what I am studying. Any doubt on this? It is constant between the two collisions or is it constant throughout? It is constant between the two collisions. But the right hand side of that expression is constant. The collision is not happening between these two. Let me substitute the value equal to u minus ee by n times t. So I will get a vector equation like this. Little minus here because electron will experience force of u minus ee by n is constant. So I will just take average of t. Is t also constant? Fine. So you are taking average. So this means average. It is just takes possible. I can change it for you. Why you have to talk to each other? Learning also so my hands at each other better.