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