各位大虾，这是我写的画图程序，请问有什么方法可以显示四条曲线的交点呢，万分感谢啊
goption reset=all;
axis1 order=(0 to 200 by 20);
symbol1 v=dot INTERPOL=join c=blue;
symbol2 v=dot INTERPOL=join c=red;
symbol1 v=dot INTERPOL=join c=green;
symbol2 v=dot INTERPOL=join c=black;
proc gplot data=a;
plot Cumpercent*F_cheap=1
     Cumpercent*F_too_cheap=2
     Cumpercent*F_expensive=3
     Cumpercent*F_too_expensive=4
    /overlay haxis=axis1 frame;
run;
quit;