The plan is heard ----- so well that we don't need to make a

因为是被动态,计划不可能自己设计自己啊。这里是用过去分词表被动的典型语句。完整的语句应该是The plan is heard which was designed so well that we don't need to make any change。which从句代替主语,也可以直接把which was省略。