Q3: Defining languages and NFAs from an alphabet

You have 2 industrial control systems S1 and S2 working concurrently. It is forbidden for S1 and S2 to be on at the same time.

Alphabet to consider:

= {On(S1), On(S2), Off(S1), Off(S2)}

A word over * is a sequence of actions.

Part A. Convert the property on sequences (above) into a language. Then, define an NFA that accepts it.

Part B. Consider a second property: S2 must power off after S1, but S2 must power on before S1. Define a language that captures this property (specifically the second property). Then, define an NFA that accepts it.

This is needed soon, so any help is appreciated! Thank you!