【快！最佳20點！】簡單英文句子問題

I have finished my homework before I call Tom or before my mother comes home.
My mother comes home after I have finished my homework.
( Here we have present perfect tense and simple present tense)
I am doing my homework when my mother comes home. (Here we have present continuous tense and simple present tense)
Perfect tense - to describe an action is done before another action starts.
Hope it is clear to you

可以有架!!

例︰While I am doing my homework, my sister is playing the computer.