For the question below i was looking for help since some parts of it i
don't get. 

For part A I import the data in matlab and then plot it using the plot
function. i get my x-axis as the number of samples which is 16384 and
then the y is the values of the signal. but i dono if i am drawing it
correct. should it be in any diff format in terms of x-axis. maybe
freq?

For part B i found the Fs by deviding the 80ms/16384. Which should be right.

For part C i get the dc componmet which is the mean of the graph from
matlab. although if my FFT graph is corrct in the next part the X(0)
will be my dc componemet.

For part D i use FFT(ABS(signal)) get a real values but i need to confirm this.

Can you please tell me what i should do here? and show me the steps
ONE BY ONE in matlab. i will need full answers and not walkthorughs
since i have an idea how to do it but i know it is not right.

files or graphs can be sent using www.yousentit.com or a link.

the signal file can be found here:
http://s59.yousendit.com/d.aspx?id=2QOB20YI5KNOG262E4UMLJAH8J

thanx a bunch in advance. a large tip will be consedered.

Question:

The attached file called ?signal? is a list of 16384 real numbers. These
numbers represent the result of sampling an audio signal for 80
milliseconds. None of the components of that signal have a frequencies
above the Nyquist threshold for the sampling rate used.

(a) Plot the signal.

(b) What was the sampling frequency?

(c) What is the D.C. component of the signal?

(d) Use the fft function and the plotting facilities of MATLAB to generate
a graph of that part of the power spectrum of this signal which contains
meaningful data.

(e) Estimate the frequencies (in kHz), amplitudes and phases (in radians)
of the principal components of the signal.

(f) Suppose a sinusoid of frequency 256kHz were added to the original
signal in the previous question before sampling. Exactly how would this
change the graph in (2d) above?