2. Properties Of PS. Y is nonempty: we have something to do Y is close: Y contain it's boundary, the array y"sy,andy"∈ Y means y∈Y o No free lunch:Y∩c{0 SOee the fo. o Free disposal: y-RTCY Oee thene lecture 1 for Chu Kechen Honors Collegelecture 1 for Chu Kechen Honors College 2.Properties of PS. • Y is nonempty: we have something to do. • Y is close: Y contain it’s boundary, • No free lunch: See the fig. • Free disposal: See the fig. the array , and means y y y Y y Y n n →   {0} n Y  + n − + y Y