口算．
2.5×0.6×0.4=    1.25×0.7×0.8=
0.1×0.2×0.3=    5.4﹣0.4×5=
0.26×0.2×50=    0.5×0.75×4=
12.5×0.1×0.8=    0.4×0.1×0.25=