Parks-McClellan FIR filter (firgr)

I'm doing a project to eliminate 60Hz of power supply from ECG signal and I want to implement by using equiripplr notch filter (Parks-McClellan). I found the (firgr) function and I tried to implement notch filter using it with fs=175Hz but I can't. Can someone help me. this my code: %%

f=0.01:0.05:1; % frequency range

a7=ones(1,20);

a7(1,14)=0; % all a7 ones except at 60Hz normalized at 0.658*pi 

d={'n' 'n' 'n' 'n' 'n' 'n' 'n' 'n' 'n' 'n' 'n' 'n' 'n' 'n' 'n' 'n' 'n' 'n' 'n' 'n'};

b7 = firgr(20,f,...
a7,d);

fvtool(b7);

[Daniel Shub]

http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer

http://www.mathworks.com/matlabcentral/answers/8626-how-do-i-get-help-on-homework-questions-on-matlab-answers