@echo off
set LOG=c:\Test.txt
echo Started at %DATE% - %TIME% >> %LOG%
echo Input param: %1 >> %LOG%
%~d1
cd %1
echo Current directory: %cd% >> %LOG%
for /f %%a IN ('dir /b *.rar') do set RAR=%%a
echo Target file: %RAR% >> %LOG%

"C:\Program Files\7-Zip\7z" e %RAR% >> %LOG%

echo. >> %LOG%
echo Finished at %DATE% - %TIME% >> %LOG%
echo. >> %LOG%