<p>Code that needs to be modified:</p><p>#include <stdio.h></p><p>#include <math.h></p><p><strong>int</strong> main(<strong>void</strong>)</p><p>{</p><p>FILE * fileout;</p><p><strong>int</strong> ix,iy,it,Nt;</p><p><strong>double</strong> newV[31][21],V[31][21],x,dx,y,dy;</p><p>fileout=fopen("buckbeak.dat","w");</p><p>printf("nEnter number of iterations ");</p><p>scanf("%d",&Nt);</p><p>dx=0.10;</p><p>dy=0.10;</p><p> </p><p><strong>for</strong>(iy=0; iy<21; iy=iy+1)</p><p>{</p><p><strong>for</strong>(ix=0; ix<31; ix=ix+1)</p><p>{</p><p>V[ix][iy]=0.0;</p><p>}</p><p>}</p><p>iy=20;</p><p><strong>for</strong> (ix=0;ix<31; ix=ix+1)</p><p> {</p><p> V[ix][iy]=8.0;</p><p> }</p><p><strong>for</strong> (it=0; it<Nt;it=it+1)</p><p>{</p><p><strong>for</strong>(iy=1; iy<20;iy=iy+1)</p><p>{</p><p><strong>for</strong>(ix=1;ix<30; ix=ix+1)</p><p>{</p><p>newV[ix][iy]=0.25*(V[ix+1][iy]+V[ix-1][iy]+V[ix][iy+1]+V[ix][iy-1]);</p><p>}</p><p>}</p><p><strong>for</strong>