Write a function that accepts two strings as the arguments, returns the characters that occur in both strings. For example, if the arguments are apple@123 and banana@#345, your program should return a@3.

5. Write a function that accepts a file name in the form of a string as the argument. Read the entire contents from the text file as a string and reverse the order of characters in the string. Append the reversed string into the same text file.

6. Write a function that accepts two lists of strings as arguments. Merge two lists together and then remove all the alphabetic letters from the merged list. Return the merged list. For example, if the two lists are [a, 2, b, 1, %, b] and [b, ?, c, a, 3, 4, g], your function should return [2, 1, %, ?, 3, 4]

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