d. One of the PLC tasks will be to activate a ventilation fan as well as switching the lighting in a room automatically on receiving specific "people presence" signals. The ventilation fan and lighting system will be activated via two separate PLC Boolean outputs. The triggering conditions to operate either system include three distinct sensors used for detecting the presence of people in the room (each giving a separate Boolean on/off signal to the PLC). The lighting system will remain on while any of the three sensors is on, while the ventilation system will switch on when at least two sensors are triggered and will switch off only when none of the sensors are triggered. A PLC program is to be created to perform such a control function. i. ii. Page 2 of 4 Create a variable allocation list for the PLC program, declaring all the variables to be used. (5 marks) Draw a simple ladder diagram program for the control function of both the lighting and ventilation fan. (8 marks)