Fluent-FFMPEG How To Add A Background Audio To A Video Which Has Sound

Question

I am using fluent-FFmpeg library to render some videos on my node js Application,

Is there a way to add a background audio to a video that already has sound, If a video doest have a sound this code works, can someone help?

  mergeFilesAsync('C:/test/rendered/sample.mp3','C:/test/rendered/a.mp4', 'C:/test/rendered/eee.mp4');


  async function mergeFilesAsync (audio, video, outputVideo) {

    ffmpeg(video)
    .addInput(audio)
    .output('bb.mp4')
    .on('end', function() {
      console.log('Finished processing');
    })
    .run();
    }
    ```
    enter code here