Add last letter prompt

tasks/cot/lastletter_prompt.txt

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+Q: Take the last letters of the words in "Elon Musk" and concatenate them.
+A: The last letter of "Elon" is "n". The last letter of "Musk" is "k'. Concatenating them is "nk". The answer is nk
+Q: Take the last letters of the words in "Larry Page" and concatenate them.
+A: The last letter of "Larry" is "y". The last letter of "Page" is "e". Concatenating them is "ye". The answer is ye.
+Q: Take the last letters of the words in "Sergey Brin" and concatenate them.
+A: The last letter of "Sergey" is "y". The last letter of "Brin" is "n". Concatenating them is "yn". The answer is
+yn.
+Q: Take the last letters of the words in "Bill Gates" and concatenate them.
+A: The last letter of "Bill" is "l". The last letter of "Gates" is "s". Concatenating them is "ls". The answer is ls.