having trouble installing Ruby on Rails with apache2 and passenger

trying to install passenger with Apache2 and ruby 2.0, and I had this line of error when I am doing:

passenger-install-apache2-module

Error:

--------------------------------------------
Compiling and installing Apache 2 module...
cd /usr/local/lib/ruby/gems/2.0.0/gems/passenger-3.0.19
/usr/local/bin/ruby /usr/local/bin/rake apache2:clean apache2 RELEASE=yes
# /usr/local/bin/ruby /usr/local/bin/rake apache2:clean apache2 RELEASE=yes
rake aborted!
cannot load such file -- rubygems/builder
(See full trace by running task with --trace)
--------------------------------------------
It looks like something went wrong

solution is update passenger :

git clone https://github.com/FooBarWidget/passenger.git
cd passenger
gem build passenger.gemspec
gem install passenger-4.0.0.rc5.gem (or type your actual built gem name)

found solution here -> http://stackoverflow.com/questions/15232856/passenger-cannot-load-such-file-rubygems-builder