DSP question. help!!!

i met some problems here. hopefully i can get the solution here.

1) A 2 th order IIR system is defined as
y-0.866 y(n −1) + 0.25y(n − 2) = x + 2x(n −1) + x(n − 2)
a) Calculate the transfer function H(z) for the difference equation.
b) Calculate the system impulse response h directly using the partial fraction
expansion method and the shift property of the z-transform.
c) Calculate and draw the frequency response |H(ej2pf)| based on the poles and zeros
positions.

how to do the part (c) question??

2) A FIR is defined by a set of poles and zeros
5 poles at z=0
Zeros at z= 1, z=1,z=-1, 0.7071-j0.7071, -0.7071-j0.7071

a) Draw the pole zero plot for the system.
b) Calculate the transfer function for the system.
c) Calculate the system impulse response.
d) Sketch the frequency representation of the system and estimate the cut off frequency
of the system.
e) Calculate the frequency representation of the system using MATLAB and estimate
the cut off frequency of the system.
f) Proof the system have linear phase.

how to do part(d), (e), and (f)

hi friend, ask me.