For this specific sentence, it feels natural to either place 了 only at A or at both places. And I think this also applies to many other sentences. So somebody someverb 了 something 了（optional） But after thinking about it a little bit more, I found exceptions. For frequently used phrases such as 写作业 玩游戏 打扫卫生 吃饭 it is the 了 in the middle of the sentence optional so 我写了作业了/我写完作业了/我写作业了（which is a bit weird, feels like your parents are doubting if you really finished the homework. ）

A。“了”加在动词后，表示did了某些事。 这句子还有地方要加字。“昨天我复印了两节课的生词。”中文的数词后要加量词。

Thanks so much

A