You are given a code:

def main_solution(x):
    return func_20(('qbkj' + 'aom'), func_15('opjd'))

Can you predict the output of `main_solution("plbrquustr")` 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": "plbrquustr"}, "ref_output": "q\u00abbok\u00bbj\u00abapo\u00bbm\u00abj\u00bb\u00abd\u00bb", "ref_code": "def main_solution(x):\n    return func_20(('qbkj' + 'aom'), func_15('opjd'))", "funcname": "main_solution"}
rule