设通话时间为X秒
1.4-0.22<0.3+0.22*(X-3*60)/60<=1.4
52.8<0.22X-39.6<=66
420
1.4-0.22<0.3+0.22*(X-3)<=1.4
0.88<0.22X-0.66<=1.1
7
0.3+0.22*(X-3)=1.4,X=8
设打了x分钟
0.3+(x-3)*0.22=1.4
x=8
0.3*3+0.22x=1.4
剩下的自己解决吧
0.3+(x-3)0.22=1.4 x=8
X小于等于(1.4-0.3)/0.22大于(1.4-0.3)/0.22 -1