EN
Let p be a prime, and let ℱ be the category of functors from the finite $𝔽_p$-vector spaces to all $𝔽_p$-vector spaces. The object Id of ℱ is the inclusion functor. Let F and G be two objects in ℱ. If F and G satisfy suitable conditions, the main result of this paper allows one to compute $Ext*_{ℱ}(Id,G∘F)$ from the knowledge of $Ext*_{ℱ}(Id,F)$ and $Ext*_{ℱ}(Id,G)$.