Multivalued maps have many applications. We consider one dimensional multivalued maps whose graphs are defined by lower and upper boundary maps. Let I = [0, 1] and let P be a partition of I into a finite number of intervals. Let τ , τu : I → I be two piecewise expanding maps on P such that τ ≤ τu. Let G ⊂ I × I be the region bounded by the graphs of τ and τu. Any map η : I → I that takes values in G is called a selector of the multivalued map defined by G. We assume that τ and τu as well as all the selectors we consider have invariant distribution functions. Let F * be a target distribution. We prove the existence of a selector η * which minimizes the functional J(η) = R I (Fη (t)−F * (t)) 2 dt, where η has invariant distribution Fη . Other results pertain to the functional J 1 (η) = R I (Pη F * (t)−F * (t)) 2 dt, where Pη is the Frobenius-Perron operator of η acting on distribution functions. We present an algorithm for finding selectors which minimize J 1 (η).