I want to show that the problem below, also known as the Knapstack Problem, is in NP (non-deterministic polynomial time). Where should I start?
Given $n$ items numbered $1$ through $n$ so that $i^{th}$ item has weight $w_i$ and value $v_i$, determine whether it is possible to select some of these items with total weight at most $W$ and total value at least $V$.