In English, you can convey the future using the present tense. Especially if, as they do here, they give you a time like "tomorrow." It's not common, but the usage exists. I bought a desk today. Tomorrow I study!
I think this is past the topic, whenever you don't see a name or a pronoun you assume is about the other person you are speaking to or about yourself if someone is speaking to you. That's just how japanese works.
It's probably because
1. Duolingo is assuming you won't be asking yourself that question and you'll be talking to or being spoken to by another person.
2. Because you are using the polite form of "will do" "します"