Cutoff frequency from the Transfer Function

[DivyaKrishnappa]

Hello everyone,

I wanted to know the cutoff frequency from the transfer function.
Transfer function of LPF is given by

(1-z^-6)^2/(1-z^-1)^2.

So the coefficients are

b = [1 0 0 0 0 0 -2 0 0 0 0 0 1]
a = [1 -2 1];

h = filter(b,a,[1 zeros(1,12)]);

How to find out cutoff frequency for this..?