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Question # 4: (15%) Device a PLC ladder Diagram that perform automatically mixing of two different chemicals in a tank: a) When start button 's' is pressed, chemical 'Al' enters the tank via A1 inlet. When it fills up to Im length of tank, inlet Al closes. b) When A1 inlet is closed, the chemical ‘A2 starts pouring in the tank through A2 inlet. A2 inlet is closed when the chemical reaches 2m of tank's length. c) After the closing of A2 inlet, stirrer 'S' will be on for 50 seconds. To mix both chemicals. + d) After stopping stirrer, it allows the mixture to drain out from ‘A3' outlet. A3 outlet should be stopped after 100s. Note: There should be an emergency stop button, when it is pressed the whole system should be stopped. S=Start button X1= Sensor at Im length of tank X2= Sensor at 2m length of tanke X= Emergency stop button Al=Chemical A1 inlet- A2= Chemical A2 inlet A3= Mixture outlet A4= Stirrer's motor To=50sec timer Ti=100sec timer e Rubrics and Marking: Totally 15 marks. Marks will be given by considering the relevance and technical completeness of the answer.