I have the following htaccess redirect:

RewriteRule ^folder/([^/]*)/ folder/index.php?a=$1 [L]

This basically redirects:
mysite.com/folder/10/

To:
mysite.com/folder/?a=10

The problem is that I also require additional variables that I do not know, E.g.
mysite.com/folder/10/?a=fff&b=eee&c=ddd

Is there a way to keep these variables within the redirect even though I do not know what they are going to be?