已知,AC:AE=5:1,BC:CD=4:1,AB;BF=6:1,那么三角形DEF的面积是三角形ABC的几分之几?

S△AEF=(AE/AC)S△ACF=(AE/AC)(AF/AB)S△ABC=(1/5)(5//6)S△ABC=(1/6)S△ABC
S△BFD=(BF/AB)S△ABD=(BF/AB)(BD/BC)S△ABC=(1/6)(3//4)S△ABC=(1/8)S△ABC
S△CDE=(CD/BC)S△BCE=(CD/BC)(BE/AC)S△ABC=(1/4)(4//5)S△ABC=(1/5)S△ABC
S△DEF=S△ABC-S△AEF-S△BFD-S△CDE=(61/120)S△ABC
61/120