"Question $3(25$ marks$)($CLO$1,$ C$5,$ PLO$1)$

a$)$ List $3$ basic elements needed in a programmable logic controller $($PLC$)$ and briefly descript ea XJ$10$ ch one of them.

b$)$ Draw a diagram to show the basic structure of a programmable logic controller $($PLC$).$ Label your diagram correctly.

c$)$ List two operations mode of a programmable logic controller and briefly explain each of them.

d$)$ In the context of process control, the controller operating on a discontinuous mode initiates a discontinuous change in the controlled variable. Name two basic operations in the discontinuous mode and explain each of them."