A.σmax=FN/Amin B.σmax=FNmax/A C.σmax=FNmin/A D.σmax=FN/Amax
A.1.2~1.4 B.1.4~1.8 C.1.8~2.8 D.2.0~3.5
A.0.7~1.0 B.1.0~1.4 C.1.4~1.8 D.2.0~2.5