试问执行以下函数会产生怎样的输出结果? 
 void demonstrate() {
StrAssign(s,'THIS IS A BOOK');
Replace(s,SubString(s,3,7),'ESE ARE');
StrAssign(t,Concat(s,'S');
StrAssign(u,'XYXYXYXYXYXY');
StrAssign(v,SubString(u,6,3));
StrAssign(w,'W');
printf('t=',t,'v=',v,'u=',Replace(u,v,w));
} //demonstrate 
 
                     
                     
             
                            