--that car must have cost a lot of money.

--that car must have cost a lot of money.--on,no._________请问否定回答用 it didn't 还是用 it can't.不过记得是这样的 must have v-ed 否定形式为：can’t / couldn’t have v-ed,为什么又用it didn't 还是与can't/couldn't have 都可以？不太明白这点，请再指教