How do i know if my mac book is working on N speed

Question

I just bought the new airport extreme and there is a software that allow to change the configuration of the mac books from G speed to N. I check that i have that software installed, but i don't know how to make it work. I don't know if it is working but i surely don't feel any difference on the speed of my network.
If somebody can help me telling me how to check is my mac book is working on N will be really appreciated.
Also, can somebody tell me how many kb/sec is N speed and G speed. And how to se at what speed I<m tranfering data between my macbook and my external drive.
thanks

Answer 1

Log out and log back in, if you haven’t done so recently. Launch the Terminal application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ If you’re running Mac OS X 10.7 or later, open LaunchPad. Click Utilities, then Terminal in the page that opens.
Step 1
Copy or drag — do not type — the line below into the Terminal window, then press return:
launchctl getenv DYLD_INSERT_LIBRARIES
Post the lines of output, if any, that appear below what you just entered (the text, please, not a screenshot.)
Step 2
Repeat with this line (triple-click anywhere in it to select the whole line):
find /Applications /System/Library/CoreServices -type d -name *.app -exec defaults read {}/Contents/Info LSEnvironment \; 2> /dev/null | grep DYLD_INSERT_LIBRARIES
The command will take a noticeable amount of time to run. Wait for a new line ending in a dollar sign (“$”) to appear.
If you get no output from either step, you're not infected with any variant of Flashback that I know of.