0.25*8.5*4
=0.25*4*8.5
=1*8.5
=8.5
2.4*1.02
=2.4*1+2.4*0.02
=2.4+0.024
=2.424
1.28*8.6+0.72*8.6
=（1.28+0.72）*8.6
=2*8.6
=17.2
12.5*0.96*0.8
=12.5*0.8*0.96
=10*0.96
=9.6