B)$ is abelian $k$-linear symmetric monoidal with unit. In particular, it is an abelian category whose Grothendieck group $K^G(G/B)$ is a commutative ring, which is isomorphic to the ring $R(B)$ of right representations of the $k$-monoid scheme $B$ on finite dimensional $k$-vector spaces: $$\xymatrix{ \cI nd_B^G:R(B) \ar[r]^<<<<<{\sim} & K