matlab - "Contour not rendered for non-finite ZData" -

i'm trying plot frequency characteristic equation using ezplot, matlab gives following warning, "contour not rendered non-finite zdata". have used command plot frequency equations warning , plot display empty , not change axis range well. can please help. appreciated.

here's code i'm using.

% transfer matrix case-i, thin rotor

clear all;  clc;  ei = 1626; l = 0.15; m = 0.44108; = 2.178*10^-4; i_p = 2.205*10^-5; itr = 0.24; i_pr = 0.479; syms p n;  f = [1 l*1i l^2/(2*ei)*1i l^3/(6*ei);     0 1 l/ei -l^2/(2*ei)*1i;     0 0 1 -l*1i;     0 0 0 l];  p = [ 1 0 0 0;     0 1 0 0;     0 -it*p^2+i_p*n*p 1 0;     -m*p^2 0 0 1];  p_r = [1 0 0 0;        0 1 0 0;        0 -itr*p^2+i_pr*n*p 1 0;        -m*p^2 0 0 1];   = f*p*f*p*f*p*f; b = p_r*f*p*f*p*f;  r = a(1,2)/a(1,4); a12_p = 0; a22_p = a(2,2)-r*a(2,4); a32_p = a(3,2)-r*a(3,4); a42_p = a(4,2)-r*a(4,4);  ap(2,2) = a22_p; ap(3,2) = a32_p; ap(4,2) = a42_p; ap(4,4) = 1;  c = b*ap;  m = [c(3,2) c(3,4);     c(4,2) c(4,4)];  sol = det(m); ezplot(sol,[-2*10^10 2*10^10]); 

the sol displayed if u ask plot doesn't display. in advance ur !! appreciated.