Let a<b<c be three integers such that a,b,c is an arithmetic progression and a,c,b is a geometric progression. What is the smallest possible value of c?<spanclass=′latex−bold′>(A)</span>−2<spanclass=′latex−bold′>(B)</span>1<spanclass=′latex−bold′>(C)</span>2<spanclass=′latex−bold′>(D)</span>4<spanclass=′latex−bold′>(E)</span>6