unmount drive windows

@echo off
REM Copy and paste this entire code in notepad and save the file with filename.bat extension
if not "%1"=="am_admin" (powershell start -verb runas '%0' am_admin & exit /b)
ECHO -----------------------------------------------------------------------------
:start
ECHO -----------------------------------------------------------------------------
ECHO Enter the letter of the drive :
ECHO -----------------------------------------------------------------------------
set /p opt=
set drive=%opt%:
echo Unmounting Drive...
mountvol %drive% /p
echo Drive Unmounted!
exit