Calculate the fundamental frequency (organ pipe)

Please help! I keep getting the wrong answer:

Calculate the fundamental frequency of a 4 meter organ pipe that is open at one end and closed at one end. Assume that the temperature is 20◦C and the speed of the sound is 344 m/s.
Answer in units of Hz

(sorry about all the periods --I have them like that because YahooAnswers won't accept the format with a bunch of spaces...)

I tried this: (but remember: it was incorrect)

lambda
---------- = 4
....2

lambda = 8

and c = f (lambda)
so,
................ c ........... 344
....... f = ---------- = ------- ... --> 43 Hz
............ lambda ...... 8

THANK YOU!!

lambda = 8x2 =16 because it is opened from one end

so f = 344 / 16 = 21.5 Hz

i am not sure by the way :D

Verify whether L = λ/2 or not .
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