计算下面各题，能简算的要写出简算过程．
①6.72+2.08×4×1.5
②12.56÷2.5÷0.4
③2.85×4.7+28.5×0.53
④9.88÷[5×（7.34﹣6.96）]
⑤2.5×3.2×1.25
⑥0.56×99．