98% of people can't solve this % * + =3 O - % - =0 = z y| =^/#w ^ = Pn(R) H>'l%,','^) has a ring structure fceN ":•(-, Z?) : C -? Set is contravariant ^(-4. Z?) = {(p : A —> i3|<p is a morphism} given that is the derived functor of *;• and sequence 0 —t i(C-y(H,; —> H';w) —t —+ 0. is exact