Stand-by indication Stand-by ON Base Stand-by OFF Protective cover 1 C Start drilling Left hand Right hand Stop drilling 4. When the two buttons "start drilling" are pressed at the same time (requires both hands of the operator for safety reason), the protective cover (activation of the relay C2) starts to lower. If the two buttons are released, the cover returns to its original position. 5. When the protective cover is brought to its final position, it is detected by sensors $2 and then the piston C1 (activation of the relay C) starts to lower, while simultaneously the drilling head starts its rotation. At this stage, the two start drilling buttons need not to be pressed because the protective cover has already been lowered. 6. Piston C1 and the drilling head press down the object until drilling is complete when sensor So activated. 7. Once So is activated, the drilling head and the protective cover return simultaneously to the initial position. Then the machine is ready to accept new object. 8. If at any time, either the two "stop drilling" buttons are pressed simultaneously or the "Stand-by OFF" button is pressed alone, the process stops and the two pistons return to the "up" position (a) Construct the ladder diagram for the operation and indicate the address clearly (10 marks)