How do I set org-mode to use racket instead of Guile?

Question

How do I set org-mode to use racket instead of Guile?

I want to use emacs,org-mode and racket to go through the SICP.

I can start Geiser, choosing Racket in the Start Geiser for scheme implementation menu.

But when I execute C-c C-c on a src block in an org file

#+BEGIN_SRC
 (print "hello world")
#+END_SRC

it tells me:

Unable to start REPL:
Searching for program: no such file or directory, guile.exe

So again, how do I set org-mode to use racket instead of Guile?

Thanks in advance for your kind help and time.

P.S

I also enable scheme in org mode and set the scheme program to be Racket

(setq scheme-program-name "C:/Program\ Files/Racket/Racket.exe")
 (org-babel-do-load-languages
      'org-babel-load-languages
      '((emacs-lisp . nil)
        (scheme . t)))

Answer 1

You leave these two lines in you .emacs file

(add-hook 'scheme-mode-hook 'geiser-mode)
(setq geiser-default-implementation 'racket)