Now in order to to look at this relationship between labour and capital and output  total product simultaneously we need to draw a 3 D diagram, alright, but because my diagrams are bad enough in 2 D what we are going to do is we are going to constrain one of these factors, right, so what we will do is we will pick a level of ou a level of capital input , right, and we will see what happens to total product as we vary labour.