How to use new file which is created by me as an output file in FFmpeg code execution ? getting E/mobile-ffmpeg: outputFile.mp3 Permission denied

I try to trimming audio from one file to another output file but I am getting trouble accessing the output file in FFmpeg to writing its shows me permission denied.

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 E/mobile-ffmpeg: /storage/emulated/0/slowmotion.mp3: **Permission denied**