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I began with a timing diagram and was asked to find the simplest sum of products form. The above is as far as I could take it. Any hint on how to go further would be appreciated. I am simply stuck. I am pretty sure it can be further simplified. But, I don't see it.
Have you been taught about Karnaugh maps? They are a very easy and visual method of simplify Boolean expressions. For the case at hand you need a 3-variable map.
If you put the minterms you found in a K-map, you will discover that this expression cannot be simplified further in a Sum of Products form. On the contrary it can be compacted a lot through the use of a XOR gate.