The period of a pendulum is given by

since Karachi is near sea level, g is larger than it is on Mt. Everest. That means the pendulum will have a larger period on Mt. Everest than it would in Karachi.
Torque = r x F
|F| = mg = 60 * 10 N = 600 N ( assuming g ~ 10m/s^2)
distance of fulcrum = torque / Force = 90/600 m = .15 m.
Efficiency is completing a task as fast a possible the the least amount of effort.