Organ Pipe

Can somebody help me?

An organ pipe is 3.00 meters in length and is open at one end with a flap at the other
end.  When the flap is open the pipe is open at both ends (open pipe).  When the flap is
closed the pipe is closed at one end and open at the other end (closed pipe).  The speed
of sound in air at 20C  is 343 m/s. 

When the pipe is closed what is the frequency of the sound produced at:
a.) the fundamental wavelength?
b.) the next highest frequency?
When the pipe is open what is the frequency of the sound produced at:
c.) the fundamental wavelength?
d.) the next highest frequency?