A railroad crossing system employs sensors, flashing lights, sounding bells, and gates to control the traffic at a railroad intersection. When a train approaches the intersection from either direction, a sensor device senses the train and communicates with the software. The software turns on the flashing yellow warning light and the sounding bell for a given period. It then changes the light to flashing red and closes the gates. After the train has left the intersection, another sensor device detects this and communicates the event to the software. The software turns off the lights and the sounding bell and opens the gates. Perform the following for the railroad crossing system:

a. Identify the hardware and software subsystems and specify the functionality of each of the subsystems.

b. Construct a system architectural design diagram to show the relationships between the subsystems.

c. Identify and formulate four safety requirements and allocate them to the subsystems. Describe how the subsystems will satisfy the safety requirements. (You can use the a table to show the safety requirements allocation)