Applescript "do shell script" variables

Hi

I'm trying to do an AppleScript and inside it run a shell script action. Something of what should be written in the shell script are variables asked before.

How can I write in the shell script variables?

Here's my script:

set sourceFolder to (choose folder with prompt "Scegli la cartella sorgente:")

set targetFolder to (choose folder with prompt "Scegli la cartella da sincronizzare:")

display dialog "Stai per sincronizzare le due cartelle selezionate, l'operazione è irreversibile. Sei sicuro?" buttons {"Annulla", "Continua"} default button 1

if button returned of result is "Continua" then

do shell script "rsync -vaE --delete [HERE GO sourceFolder VARIABLE] [HERE GO targetFolder VARIABLE]"

else

error "Operazione annullata dall'utente" number -128

end if