You are given a code:

def main_solution(x):
    return func_20(func_15('xrtgvu'), func_9('vlijmo'))

Can you predict the output of `main_solution("xpxb")` 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": "xpxb"}, "ref_output": "\u00abvxl\u00bbi\u00abjrm\u00bbo\u00abotm\u00bbj\u00abigl\u00bbv\u00abv\u00bb\u00abu\u00bb", "ref_code": "def main_solution(x):\n    return func_20(func_15('xrtgvu'), func_9('vlijmo'))", "funcname": "main_solution"}
rule