You are given a code:

def main_solution(x):
    return func_20(func_20('bka', x), func_15(x))

Can you predict the output of `main_solution("xaptlxzruw")` without writing any code? Please reason and put your final answer in the following json format: {"output": <your output>}, where <your output> should be the final string.
user
{"ref_input": {"x": "xaptlxzruw"}, "ref_output": "b\u00abxxk\u00bba\u00abaap\u00bbt\u00ablpx\u00bbz\u00abrtu\u00bbw\u00abl\u00bb\u00abx\u00bb\u00abz\u00bb\u00abr\u00bb\u00abu\u00bb\u00abw\u00bb", "ref_code": "def main_solution(x):\n    return func_20(func_20('bka', x), func_15(x))", "funcname": "main_solution"}
rule