Given `m_(A) = 30 kg, m_(B) = 10 kg, m_(C) = 20 kg`. Between a & B `mu_(1) = 0.3`, between B & C `mu_(2) = 0.2` & between C & ground `mu_(3) = 0.1`. The least horizontal force F to start motion of ant part of the system of three blocks resting upon one another as shown below is :
(Take `g = 10m//s^(2)`)
A. 90 N
B. 80 N
C. 60 N
D. 150 N