Last night you should've made a wish at 9:21 pm because it was - the 21st minute
- of the 21st hour
- of the 21st day
- of the 21st year
- of the 21st century

1. define independent-set as the problem that takes a graph g and an integer k and asks whether g contains an independent set of vertices of size k. that is, g contains a set i of vertices of size k such that, for any v and w in i, there is no edge (v,w) in g. show that independent-set is np-complete.