计算下面各题（能简算的要简算）．
①4×0.8×2.5×12.5             ②÷[1﹣（+）]          ③（2.8+3.85÷3.5）×4.6         
④6.5×1.83+0.17×6.5          ⑤（+）×8+            ⑥÷[×（0.4+）]．