More んです marking please :)

Hi there, I've continued my work with ~んです and would like my work marked please

Q: どうしてアルバイトをしているんですか。

My Answer: たくさんかねをもちたいんです。

Q: どうしてきのうじゅぎょうをサボったんですか。

My answer: ともだちとおさかにいったんです。

Q: どうしてつかれているんですか。

My answer: きのうはごごいちじにねったんです。

Q: どうしてきんちょうしているんですか。

My answer: きょうはしけんがあるんです。

Thank you!

1. There are different ways to express this (with ほしい;おかねがたくさんほしい, etc.), but without changing your answer too much, I think this should be おかねをたくさんもちたいんです。たくさん just before the verb feels a bit better to me in this sentence.
3.ごぜん is AM, you probably meant that instead of ごご.

By the way, is there some reason why you're writing all of this in katakana only? It doesn't hurt to start using kanji early. All of these words are pretty common, too.
Edit: Also, do you have to strictly write sentences with んです? I'm asking because I believe that it would make a bit more sense if you answered with からです since you're answering to "どうして", i.e., giving reasons.

Thanks for marking. Yes, I have to use んですfor this exercise and don't use kanji yet as I don't feel confident enough. I touched upon kanji, but want to follow the learning sequences in my book first. Kanji is taught in later sections.

おおさか, not おさか.

Check again the past form of ねる(寝る).