User input assigned to variable in AppleScript then passed to "do shell script" command How do I grab input from the user in AppleScript and then pass the result of the variable to a do shell script command from within AppleScript itself?

For example, the user would type the answer foo to the following dialog box:

display dialog "Please enter your username" default answer ""
set the userID to the text returned of the result
do shell script "rm -rf /Users/$userID/.Trash/*" with administrator privileges


So in this instance, if I were to incorporate the answer of foo in lieu of $userID, it would read as the following when it executes the command:

display dialog "Please enter your username" default answer ""
set the userID to the text returned of the result
do shell script "rm -rf /Users/foo/.Trash/*" with administrator privileges


How do I pass that variable I grabbed earlier, in this case it would be $userID and incorporate it into the middle of the shell script call that I have made just above.
This assigns the name entered to the variable answer.

display dialog "What's your name?" default answer ""
set answer to text returned of result
display dialog "Your name is " &amp; answer