Ubuntu :: Extract Audio And Then Convert To Mp4 Format?

I'm trying to extract audio and then convert to mp4 format a bunch of flv files downloaded from internet. There are three files I intend to use ffmpeg in the following options:

ffmpeg -i input.flv -acodec copy output.mp3
and
ffmpeg -i "input.flv" -f mp4 -vcodec libxvid -s 640x360 -b 768kb -r 25 -aspect 16:9 -acodec libfaac -ab 96kb -ar 44100 -ac 2 "output.mp4"
So I started writing a script like this:
#!/bin/bash -x
cd /home/koli/exp

[Code]....