gnome--terminal -e option not executing?

I want to open my terminal with some commands executed in it on bootup. So I wrote a script with following line in it:

gnome-terminal --tab -t "MyPC" -e "sh -c 'firefox &;exec bash'" --tab -t "MYPC2" -e "sh -c 'ls;exec bash'"

In this firefox & is not executing, however if I write only firefox it executes. So only the second tab is opening not the first one

I know it's some spacing issue. If I write just ls that also executes.

What is the correct syntax? Why is it not taking spacing??