How to set RUBY EXECUTABLE path in Ruby Gems Environment

I have ruby 2 version in my Mac which are 1.8.6 and 1.8.7. I would like to set Rubygems environment to point to Ruby 1.8.7.

Anyone know this issure???

ubyGems Environment:   - RUBYGEMS VERSION: 1.3.5   - RUBY VERSION: 1.8.6 (2008-08-11 patchlevel 287) [universal- darwin9.0]   - INSTALLATION DIRECTORY: /Library/Ruby/Gems/1.8   - RUBY EXECUTABLE: /System/Library/Frameworks/Ruby.framework/ Versions/1.8/usr/bin/ruby   - EXECUTABLE DIRECTORY: /usr/bin   - RUBYGEMS PLATFORMS:     - ruby     - universal-darwin-9   - GEM PATHS:      - /Library/Ruby/Gems/1.8      - /Users/panu/.gem/ruby/1.8      - /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ ruby/gems/1.8   - GEM CONFIGURATION:      - :update_sources => true      - :verbose => true      - :benchmark => false      - :backtrace => false      - :bulk_threshold => 1000      - :sources => ["RubyGems.org | your community gem host, "http:// gems.github.com/"]   - REMOTE SOURCES:      - http://gems.rubyforge.org/      - http://gems.github.com/