For each positive integerk, we consider the setA k of all ordered pairs [a, b] such that in everyk-graph withn vertices andm edges some set of at mostam+bn vertices meets all the edges. We show that eachA k withk≥2 has infinitely many extreme points and conjecture that, for every positive e, it has only finitely many extreme points [a, b] witha≥e. With the extreme points ordered by the first coordinate, we identify the last two extreme points of everyA k , identify the last three extreme points ofA 3, and describeA 2 completely. A by-product of our arguments is a new algorithmic proof of Turan's theorem.