作函数图像:
y=0.03(x-60000)(0≥x≥36000);y=0.1(x-60000)-2520(36000≥x≥144000);y=0.2(x-60000)-16920(144000≥x≥300000);y=0.25(x-60000)-31920(300000≥x≥420000);y=0.3(x-60000)-52920(420000≥x≥660000);y=0.35(x-60000)-85920(660000≥x≥960000);y=0.45(x-60000)-181920(960000≥x);