The brake pedal of a car is pressed with a force of 30 N. The lever (a = 20 cm, b = 4cm) - see the figure below - transmits the force to the smaller piston of the brake oil pipe. The larger piston on the other side of the pipe applies force 
on the brake linings. What is this force?
The areas of the smaller and larger pistons are given as 
and 
respectively.
Hydraulic brake
.
