Question. Were Greeks essential to crafting Egyptian Lighthouse of Alexandria?
Answer. yes
What step-by-step reasoning justifies that answer?

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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Reasoning: The Lighthouse of Alexandria was an impressive monument in Egypt. The Lighthouse of Alexandria was built by pharaoh Ptolemy II. Ptolemy II was the son of Ptolemy I Soter. Ptolemy I Soter was a Greek bodyguard of Alexander the Great and became pharaoh of Egypt.