Hi: Could anyone help with the following problem?

Please see the attached file "a.org" with its text export "a.txt" (from C-c C-e a).

Test 1 is using "buffer-wide header arguments" BUT the evaluation result is not inserted into the exported file.  I am following the Org Manual section 14.8.1 (Using header arguments).

Test 2 is using "code block specific header arguments" and works as expected. 
 
For this test, I start emacs with "emacs -Q", use org-version 7.8.11, and enabled " Org Confirm Babel Evaluate" and add R to "Org Babel Load Languages".

Thanks a lot for your hel p!

Sincerely,
Feiming Chen

------------------------------------------------------------------------


Emacs  : GNU Emacs 24.1.1 (i686-pc-linux-gnu, GTK+ Version 2.22.0)
 of 2012-08-13 on fmc.work
Package: Org-mode version 7.8.11

current state:
==============
(setq
 org-export-blocks '((src org-babel-exp-src-block nil)
             (export-comment org-export-blocks-format-comment t)
             (ditaa org-export-blocks-format-ditaa nil)
             (dot org-export-blocks-format-dot nil))
 org-ctrl-c-ctrl-c-hook '(org-babel-hash-at-point
              org-babel-execute-safely-maybe)
 org-export-preprocess-before-selecting-backend-code-hook '(org-beamer-select -beamer-code)
 org-tab-first-hook '(org-hide-block-toggle-maybe
              org-src-native-tab-command-maybe
              org-babel-hide-result-toggle-maybe)
 org-cycle-hook '(org-cycle-hide-archived-subtrees org-cycle-hide-drawers
          org-cycle-show-empty-lines
          org-optimize-window-after-visibility-change)
 org-agenda-before-write-hook '(org-agenda-add-entry-text)
 org-confirm-babel-evaluate nil
 org-speed-command-hook '(org-speed-command-default-hook
              org-babel-speed-command-hook)
 org-babel-pre-tangle-hook '(save-buffer)
 org-occur-hook '(org-first-headline-recenter)
 org-export-interblocks '( (src org-babel-exp-non-block-elements))
 org-metaup-hook '(org-babel-load-in-session-maybe)
 org-reveal-start-hook '(org-decrypt-entry)
 org-confirm-elisp-link-function 'yes-or-no-p
 org-export-latex-format-toc-function 'org-export-latex-format-toc-default
 org-export-preprocess-before-normalizing-links-hook '(org-remove-file-link-modifiers)
 org-clock-out-hook '(org-clock-remove-empty-clock-drawer)
 org-export-first-hook '(org-beamer-initialize-open-trackers)
 org-mode-hook '(#[nil
           "\305\306    >\203