Replace a string in file using shell script

Suppose my file a.conf is as following

Include /1
Include /2
Include /3

I want to replace "Include /2" with a new line, I write the code in .sh file : 

line="Include \\/2"
rep=""

sed "s/${line}/${rep}/g" /root/new_scripts/a.conf > /tmp/a.conf-new

mv /tmp/a.conf-new /root/new_scripts/a.conf