 So this is just a random aside as we were talking about tree growth. It turns out that tree growth is how I got into science in The the 80s and 90s together with my friends Paul and Mark We participated in the German science competition. Well, we were Simulating the growth of trees and so I think it's a fun link there. So Let's now move towards more meaningful trees. You saw how trees can be grown and Let's look at how Q is calculated in practice and understand the calculation of Q