Shell Programming and Scripting

Hello guys,
I am trying to run an installer through my script. Whatever yes/no or values required during the installation is provided by an answer file (answ.txt)
./install < /var/answ.txt

Now, during the installation, it asks for:
1) press return to continue
2) press 3 and hit enter
3) press yes to change [no]?
I want to change it to yes.
now my answ.txt file is:
echo "\n\n3\nyes" > /var/answ.txt
and when i echo it,
#echo "\n\n3\nyes" > /var/answ.txt

3
yes
#
But for some reasons it is not picking the right on from this file.. any suggestion???
thanks in advance.