Hi guys, how to fix this problems?

L-65; C-10; a-15: x-linspace(0,65,1); t-linspace(0,10,1); [x,Tl-meshgrid(x,t) an-@(n)sin(pi*n*a/L)./(Ln.(2)-an.(2)) #xt-e(n) cos (c*n*pi*T/L). *sin (n*pi*X/L) ; U (2*L (2)/(pi*(2) *a))ones(size(X)) for m-1:20 Jommand windoW ass5 Error using surf (Line 82) Z must be a matrix, not a scalar or vector. Error in ass5 (Line 13) surf(x,t,U) U-U+an (m)*fxt(m); end surf(x,t,U) xlabel('x'),ylabel'yzlabel('u') L-65; C-10; a-15: x-linspace(0,65,1); t-linspace(0,10,1); [x,Tl-meshgrid(x,t) an-@(n)sin(pi*n*a/L)./(Ln.(2)-an.(2)) #xt-e(n) cos (c*n*pi*T/L). *sin (n*pi*X/L) ; U (2*L (2)/(pi*(2) *a))ones(size(X)) for m-1:20 Jommand windoW ass5 Error using surf (Line 82) Z must be a matrix, not a scalar or vector. Error in ass5 (Line 13) surf(x,t,U) U-U+an (m)*fxt(m); end surf(x,t,U) xlabel('x'),ylabel'yzlabel('u')