Doubt about Factoring



Hello,

    I am having the following problem in Maxima. I have an expression 
which has a format like this:
f:a*b+b*c+a*c;
    In fact, my expression is waaaay larger than this, this is only to 
exemplify.
    I would like to tell maxima that "c" is an important variable and i 
want it to be "factored out" of the expression, like this:
f:a*b+(a+b)*c;
    How can I accomplish this?

Thanks for your help!

Felipe