Please Help Me With .htaccess file

I would like to have visits to my http://example.com/robots.txt page return the same contents as my index page but with the url name http://example.com/robots.txt page. I have seen this done so I know it is possible. I just need help with the coding of the file. I have pasted my current .htaccess file below. This file also resolves www and non www requests to non www requests. Thank you for your help.

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress