function b = backT(engine, f, t)if t==1  [b.clpot, seppot] = distribute_evidence(engine.jtree_engine1, f.clpot, f.seppot);else  [b.clpot, seppot] = distribute_evidence(engine.jtree_engine, f.clpot, f.seppot);endfor c=1:length(b.clpot)  [b.clpot{c}, ll(c)] = normalize_pot(b.clpot{c});endb.t = t;