You are given a code:

def main_solution(x):
    return func_20(func_5('roy', 'bnqr'), func_15('usxld'))

Can you predict the output of `main_solution("ustfbvw")` 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": "ustfbvw"}, "ref_output": "b\u00abnuq\u00bbr\u00abrso\u00bby\u00abx\u00bb\u00abl\u00bb\u00abd\u00bb", "ref_code": "def main_solution(x):\n    return func_20(func_5('roy', 'bnqr'), func_15('usxld'))", "funcname": "main_solution"}
rule